Path object where different vertices use different transforms?

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

···

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

I don't think the transformations framework is going to be of much help for automating this. You seem to be suggesting an x-axis where the center is in data coords and the width is in axes coords. Once you've added the two together, it will be impossible to separate them.

I think the path of least resistance will be for you to create a new artist class and override the draw method, such that you can do all the necessary calculations based on the current values of the axes and data transforms on every draw.

There's an example of creating a custom artist in api/line_with_text.py... Then it's just writing a draw method to do what you need to do -- you should be able to get at the axes transformations through self.axes.transAxes and self.axes.transData. I'm a bit busy today to really work that through, but hopefully that's enough to get you started.

Mike

Uri Laserson wrote:

···

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do all this very simply by using a PolyCollection, with the vertices in axes coordinates and the offset in data coordinates.

Eric

···

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

If I understand correctly, the top and bottom of the box are in data coordinates, the x-center of the box is in data coordinates, only the width of the box is in axes coordinates. Is that correct? If so, a PolyCollection won't be able to do this (directly), since that would require both the width and height to be in axes coordinates.

Mike

Eric Firing wrote:

···

Uri Laserson wrote:
  

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?
    
I must be missing something, because I still don't see why you can't do all this very simply by using a PolyCollection, with the vertices in axes coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the width
of the box is in axes coordinates. Is that correct? If so, a

That's exactly correct.

PolyCollection won't be able to do this (directly), since that would require
both the width and height to be in axes coordinates.

In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

Uri

···

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the width
of the box is in axes coordinates. Is that correct? If so, a

That's exactly correct.

I personally think that a box, whose height has a physical meaning (in
data coordinate) while its width does not, is not a good
representation of your data. A vertical line or something like
errorbar seems to be more suitable to me.

PolyCollection won't be able to do this (directly), since that would require
both the width and height to be in axes coordinates.

In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

As Mike has explained, the transform trick (blended or not) won't
work. The width and y-center will be always transformed with the same
transform, which is not what you want. I think you need to create a
custom patch class for this to work. One option seems to subclass the
Rectangle class and overide the _update_patch_transform method. The
patch transform is used to transform a unit rectangle to a rectangle
in data coordinate (or whatever coordinate the patch uses), i.e., you
need to calculate the coordinate of the box in the data coordinate(or
whatever coordinate the patch uses).

-JJ

···

On Mon, Sep 28, 2009 at 4:15 PM, Uri Laserson <laserson@...1166...> wrote:

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
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Is the attached sort of what you want? It defines a custom rectangle by (x, w, y1, y2) and overrides the get_transform of the patch to update itself at draw time.

Mike

Uri Laserson wrote:

custom_box.py (1021 Bytes)

···

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:
  

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the width
of the box is in axes coordinates. Is that correct? If so, a
    
That's exactly correct.

PolyCollection won't be able to do this (directly), since that would require
both the width and height to be in axes coordinates.
    
In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

Uri

Mike

Eric Firing wrote:
    

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Hi Mike,

This is definitely on the right track. Thanks a lot for writing it
out. When I change the view limits, indeed the width stays constant
while the height gets rescaled. However, when I try to change to a
logarithmic axis, I get the following errors. Again, excuse my
ignorance, but I am not sure where exactly the offense is and how to
fix it.

In [57]: ax.set_xscale('log')

In [58]: plt.draw()
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

···

---------------------------------------------------------------------------
TypeError Traceback (most recent call last)

/Users/laserson/Desktop/<ipython console> in <module>()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/pyplot.pyc
in draw()
    348 def draw():
    349 'redraw the current figure'
--> 350 get_current_fig_manager().canvas.draw()
    351
    352 @docstring.copy_dedent(Figure.savefig)

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_tkagg.pyc
in draw(self)
    213
    214 def draw(self):
--> 215 FigureCanvasAgg.draw(self)
    216 tkagg.blit(self._tkphoto, self.renderer._renderer, colormode=2)
    217 self._master.update_idletasks()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_agg.pyc
in draw(self)
    376
    377 self.renderer = self.get_renderer()
--> 378 self.figure.draw(self.renderer)
    379
    380 def get_renderer(self):

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
     53 def draw_wrapper(artist, renderer, *kl):
     54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
     56 after(artist, renderer)
     57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/figure.pyc
in draw(self, renderer)
    770
    771 # render the axes
--> 772 for a in self.axes: a.draw(renderer)
    773
    774 # render the figure text

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
     53 def draw_wrapper(artist, renderer, *kl):
     54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
     56 after(artist, renderer)
     57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/axes.pyc
in draw(self, renderer, inframe)
   1743
   1744 for zorder, i, a in dsu:
-> 1745 a.draw(renderer)
   1746
   1747 renderer.close_group('axes')

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
     53 def draw_wrapper(artist, renderer, *kl):
     54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
     56 after(artist, renderer)
     57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/patches.pyc
in draw(self, renderer)
    353
    354 path = self.get_path()
--> 355 transform = self.get_transform()
    356 tpath = transform.transform_path_non_affine(path)
    357 affine = transform.get_affine()

/Users/laserson/Desktop/testMyPatch.py in get_transform(self)
     22 box = [[self.x, self.y1],
     23 [self.x, self.y2]]
---> 24 box = self.axes.transData.transform(box)
     25
     26 # Get the width as a fraction of the axes width

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
   1893 def transform(self, points):
   1894 return self._b.transform(
-> 1895 self._a.transform(points))
   1896 transform.__doc__ = Transform.transform.__doc__
   1897

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
   1721 x_points = x.transform(points)[:, 0:1]
   1722 else:
-> 1723 x_points = x.transform(points[:, 0])
   1724 x_points = x_points.reshape((len(x_points), 1))
   1725

TypeError: list indices must be integers

On Mon, Sep 28, 2009 at 16:56, Michael Droettboom <mdroe@...86...> wrote:

Is the attached sort of what you want? It defines a custom rectangle by (x,
w, y1, y2) and overrides the get_transform of the patch to update itself at
draw time.

Mike

Uri Laserson wrote:

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the
width
of the box is in axes coordinates. Is that correct? If so, a

That's exactly correct.

PolyCollection won't be able to do this (directly), since that would
require
both the width and height to be in axes coordinates.

In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in
axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and
stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register
now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import matplotlib.transforms as mtransforms
import matplotlib.path as mpath

class MyBox(mpatches.Patch):

def __init__(self, x, w, y1, y2, **kwargs):
self.x = x
self.w = w
self.y1 = y1
self.y2 = y2
mpatches.Patch.__init__(self, **kwargs)

def get_path(self):
return mpath.Path.unit_rectangle()

def get_transform(self):

 \# Transform the data\-relative values
 box = \[\[self\.x, self\.y1\],
        \[self\.x, self\.y2\]\]
 box = self\.axes\.transData\.transform\(box\)

 \# Get the width as a fraction of the axes width
 w = self\.w \* self\.axes\.bbox\.width / 2\.0

 \# Add it to the data\-transformed coordinates
 box\[0\]\[0\] \-= w
 box\[1\]\[0\] \+= w

 return mtransforms\.BboxTransformTo\(mtransforms\.Bbox\(box\)\)

fig = plt.figure()
ax = fig.add_subplot(111)
patch = MyBox(0, 0.1, 0.5, 1.5)
ax.add_patch(patch)
ax.set_xlim((-1, 1))
ax.set_ylim((0, 2))

plt.show()

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

I personally think that a box, whose height has a physical meaning (in
data coordinate) while its width does not, is not a good
representation of your data. A vertical line or something like
errorbar seems to be more suitable to me.

I agree, and if you're a fan of Edward Tufte, then you definitely
agree. In his book, he takes the simple Tukey-style boxplot and turns
it into a 1-dimension object, in line with the type of data it's
representing. However, I still want to implement something that's a
bit more traditional, which is why I wanted to pick an arbitrary width
for the boxes that stay invariant regardless of the scale that I use.

As Mike has explained, the transform trick (blended or not) won't
work. The width and y-center will be always transformed with the same
transform, which is not what you want. I think you need to create a
custom patch class for this to work. One option seems to subclass the
Rectangle class and overide the _update_patch_transform method. The
patch transform is used to transform a unit rectangle to a rectangle
in data coordinate (or whatever coordinate the patch uses), i.e., you
need to calculate the coordinate of the box in the data coordinate(or
whatever coordinate the patch uses).

Could you possibly explain exactly what is going on and how this
structurally differs from the approach that Mike posted?

In Mike's code, he uses BboxTransformTo using the box he created in
display coords. So this takes a unit square and spits out the box
that I specify when I instantiate the custom patch (using data coords
for x and y and axes coords for w). What is called to actually draw
the box (i.e., when I execute plt.draw())? Is that get_path()? So
basically, whenever MPL wants to draw a patch, does it always call
get_path() and then runs it through whatever is returned from
get_transform() to get the final shape in display coords?

So how does this relate to the strategy that you are advocating? Is
_update_patch_transform somehow a synonym for what I described in the
paragraph above? I don't know where that fits into the picture.

It may be useful to add something to the "Working With Tranformations"
section or the "Transformation Tutorial" about what is minimally
necessary to override for a custom patch. I have been playing around
with MPL for some time now (albeit I don't have much computer
visualization/graphics experience) and still have only a fuzzy idea of
what order things are called in and what the overall
strategy/structure of the system is like.

Uri

···

On Mon, Sep 28, 2009 at 16:53, Jae-Joon Lee <lee.j.joon@...287...> wrote:

-JJ

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
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--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

Could you possibly explain exactly what is going on and how this
structurally differs from the approach that Mike posted?

In Mike's code, he uses BboxTransformTo using the box he created in
display coords. So this takes a unit square and spits out the box
that I specify when I instantiate the custom patch (using data coords
for x and y and axes coords for w). What is called to actually draw
the box (i.e., when I execute plt.draw())? Is that get_path()? So
basically, whenever MPL wants to draw a patch, does it always call
get_path() and then runs it through whatever is returned from
get_transform() to get the final shape in display coords?

Your understanding is basically right. When plt.draw(or any
equivalent) is called, the draw methods of each artists are called.
And the draw method of the Patch class, in general, calls the get_path
and get_transform, while details can be different.

So how does this relate to the strategy that you are advocating? Is
_update_patch_transform somehow a synonym for what I described in the
paragraph above? I don't know where that fits into the picture.

Yes, for the Rectangle class, its get_transform method returns a
combined transform of patch_transform + default_artist_transform,
where the patch_transform is used to transform the unit rectangle to
the data coordinate. So, the basic idea is very similar to Mike's
implementation, while Mike's should be more efficient as it transforms
the unit rectangle directly to the canvas coordinate.

It may be useful to add something to the "Working With Tranformations"
section or the "Transformation Tutorial" about what is minimally
necessary to override for a custom patch. I have been playing around
with MPL for some time now (albeit I don't have much computer
visualization/graphics experience) and still have only a fuzzy idea of
what order things are called in and what the overall
strategy/structure of the system is like.

Well, right now, I guess the source code is your best tutor (which was
and still is for me). You may start with the mpatches.Patch that
Mike's MyBox inherit from. And any contribution will be greatly
appreciated!

-JJ

···

Uri

-JJ

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
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_______________________________________________
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

The exception will go away if you explicitly use np.array as below.

     box = np.array([[self.x, self.y1],
                     [self.x, self.y2]])

However, note that Mike's example has x-center at 0.

-JJ

···

On Mon, Sep 28, 2009 at 6:41 PM, Uri Laserson <laserson@...1166...> wrote:

Hi Mike,

This is definitely on the right track. Thanks a lot for writing it
out. When I change the view limits, indeed the width stays constant
while the height gets rescaled. However, when I try to change to a
logarithmic axis, I get the following errors. Again, excuse my
ignorance, but I am not sure where exactly the offense is and how to
fix it.

In [57]: ax.set_xscale('log')

In [58]: plt.draw()
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

---------------------------------------------------------------------------
TypeError Traceback (most recent call last)

/Users/laserson/Desktop/<ipython console> in <module>()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/pyplot.pyc
in draw()
348 def draw():
349 'redraw the current figure'
--> 350 get_current_fig_manager().canvas.draw()
351
352 @docstring.copy_dedent(Figure.savefig)

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_tkagg.pyc
in draw(self)
213
214 def draw(self):
--> 215 FigureCanvasAgg.draw(self)
216 tkagg.blit(self._tkphoto, self.renderer._renderer, colormode=2)
217 self._master.update_idletasks()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_agg.pyc
in draw(self)
376
377 self.renderer = self.get_renderer()
--> 378 self.figure.draw(self.renderer)
379
380 def get_renderer(self):

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/figure.pyc
in draw(self, renderer)
770
771 # render the axes
--> 772 for a in self.axes: a.draw(renderer)
773
774 # render the figure text

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/axes.pyc
in draw(self, renderer, inframe)
1743
1744 for zorder, i, a in dsu:
-> 1745 a.draw(renderer)
1746
1747 renderer.close_group('axes')

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/patches.pyc
in draw(self, renderer)
353
354 path = self.get_path()
--> 355 transform = self.get_transform()
356 tpath = transform.transform_path_non_affine(path)
357 affine = transform.get_affine()

/Users/laserson/Desktop/testMyPatch.py in get_transform(self)
22 box = [[self.x, self.y1],
23 [self.x, self.y2]]
---> 24 box = self.axes.transData.transform(box)
25
26 # Get the width as a fraction of the axes width

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
1893 def transform(self, points):
1894 return self._b.transform(
-> 1895 self._a.transform(points))
1896 transform.__doc__ = Transform.transform.__doc__
1897

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
1721 x_points = x.transform(points)[:, 0:1]
1722 else:
-> 1723 x_points = x.transform(points[:, 0])
1724 x_points = x_points.reshape((len(x_points), 1))
1725

TypeError: list indices must be integers

On Mon, Sep 28, 2009 at 16:56, Michael Droettboom <mdroe@...86...> wrote:

Is the attached sort of what you want? It defines a custom rectangle by (x,
w, y1, y2) and overrides the get_transform of the patch to update itself at
draw time.

Mike

Uri Laserson wrote:

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the
width
of the box is in axes coordinates. Is that correct? If so, a

That's exactly correct.

PolyCollection won't be able to do this (directly), since that would
require
both the width and height to be in axes coordinates.

In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in
axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and
stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register
now&#33;
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_______________________________________________
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--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import matplotlib.transforms as mtransforms
import matplotlib.path as mpath

class MyBox(mpatches.Patch):

def __init__(self, x, w, y1, y2, **kwargs):
self.x = x
self.w = w
self.y1 = y1
self.y2 = y2
mpatches.Patch.__init__(self, **kwargs)

def get_path(self):
return mpath.Path.unit_rectangle()

def get_transform(self):

 \# Transform the data\-relative values
 box = \[\[self\.x, self\.y1\],
        \[self\.x, self\.y2\]\]
 box = self\.axes\.transData\.transform\(box\)

 \# Get the width as a fraction of the axes width
 w = self\.w \* self\.axes\.bbox\.width / 2\.0

 \# Add it to the data\-transformed coordinates
 box\[0\]\[0\] \-= w
 box\[1\]\[0\] \+= w

 return mtransforms\.BboxTransformTo\(mtransforms\.Bbox\(box\)\)

fig = plt.figure()
ax = fig.add_subplot(111)
patch = MyBox(0, 0.1, 0.5, 1.5)
ax.add_patch(patch)
ax.set_xlim((-1, 1))
ax.set_ylim((0, 2))

plt.show()

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
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Thanks so much for all the help! If my effort will produce something
nice, I'll forward it on...

Uri

···

On Mon, Sep 28, 2009 at 23:38, Jae-Joon Lee <lee.j.joon@...287...> wrote:

The exception will go away if you explicitly use np.array as below.

box = np\.array\(\[\[self\.x, self\.y1\],
                \[self\.x, self\.y2\]\]\)

However, note that Mike's example has x-center at 0.

-JJ

On Mon, Sep 28, 2009 at 6:41 PM, Uri Laserson <laserson@...1166...> wrote:

Hi Mike,

This is definitely on the right track. Thanks a lot for writing it
out. When I change the view limits, indeed the width stays constant
while the height gets rescaled. However, when I try to change to a
logarithmic axis, I get the following errors. Again, excuse my
ignorance, but I am not sure where exactly the offense is and how to
fix it.

In [57]: ax.set_xscale('log')

In [58]: plt.draw()
ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

ERROR: An unexpected error occurred while tokenizing input
The following traceback may be corrupted or invalid
The error message is: ('EOF in multi-line statement', (568, 0))

---------------------------------------------------------------------------
TypeError Traceback (most recent call last)

/Users/laserson/Desktop/<ipython console> in <module>()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/pyplot.pyc
in draw()
348 def draw():
349 'redraw the current figure'
--> 350 get_current_fig_manager().canvas.draw()
351
352 @docstring.copy_dedent(Figure.savefig)

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_tkagg.pyc
in draw(self)
213
214 def draw(self):
--> 215 FigureCanvasAgg.draw(self)
216 tkagg.blit(self._tkphoto, self.renderer._renderer, colormode=2)
217 self._master.update_idletasks()

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/backends/backend_agg.pyc
in draw(self)
376
377 self.renderer = self.get_renderer()
--> 378 self.figure.draw(self.renderer)
379
380 def get_renderer(self):

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/figure.pyc
in draw(self, renderer)
770
771 # render the axes
--> 772 for a in self.axes: a.draw(renderer)
773
774 # render the figure text

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/axes.pyc
in draw(self, renderer, inframe)
1743
1744 for zorder, i, a in dsu:
-> 1745 a.draw(renderer)
1746
1747 renderer.close_group('axes')

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/artist.pyc
in draw_wrapper(artist, renderer, *kl)
53 def draw_wrapper(artist, renderer, *kl):
54 before(artist, renderer)
---> 55 draw(artist, renderer, *kl)
56 after(artist, renderer)
57

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/patches.pyc
in draw(self, renderer)
353
354 path = self.get_path()
--> 355 transform = self.get_transform()
356 tpath = transform.transform_path_non_affine(path)
357 affine = transform.get_affine()

/Users/laserson/Desktop/testMyPatch.py in get_transform(self)
22 box = [[self.x, self.y1],
23 [self.x, self.y2]]
---> 24 box = self.axes.transData.transform(box)
25
26 # Get the width as a fraction of the axes width

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
1893 def transform(self, points):
1894 return self._b.transform(
-> 1895 self._a.transform(points))
1896 transform.__doc__ = Transform.transform.__doc__
1897

/Library/Frameworks/Python.framework/Versions/4.3.0/lib/python2.5/site-packages/matplotlib/transforms.pyc
in transform(self, points)
1721 x_points = x.transform(points)[:, 0:1]
1722 else:
-> 1723 x_points = x.transform(points[:, 0])
1724 x_points = x_points.reshape((len(x_points), 1))
1725

TypeError: list indices must be integers

On Mon, Sep 28, 2009 at 16:56, Michael Droettboom <mdroe@...86...> wrote:

Is the attached sort of what you want? It defines a custom rectangle by (x,
w, y1, y2) and overrides the get_transform of the patch to update itself at
draw time.

Mike

Uri Laserson wrote:

On Mon, Sep 28, 2009 at 16:03, Michael Droettboom <mdroe@...86...> wrote:

If I understand correctly, the top and bottom of the box are in data
coordinates, the x-center of the box is in data coordinates, only the
width
of the box is in axes coordinates. Is that correct? If so, a

That's exactly correct.

PolyCollection won't be able to do this (directly), since that would
require
both the width and height to be in axes coordinates.

In principle, could you use a blended tranform for that? Eitherway, I
don't think it would work, because the patch objects would be drawn to
specific Axes coords. If the scale is changed (e.g, by switching to
log scale), then what would prompt the Axes coords to be recalculated?
I was thinking earlier that I could compose the transData and
transAxes.inverse transforms to recalculate where the new Axes coord
should be, but Mike thought this approach would fail (though I'm still
not exactly sure why, no doubt because of my own ignorance).

Uri

Mike

Eric Firing wrote:

Uri Laserson wrote:

Is it possible to specify a path object that will use different
transforms for different vertices?

This is again related to plotting a box whose height is specified by
data coords, but whose width is a constant in axes coords regardless
of scale (so linear and log x-scales would produce a box of the same
width).

Ideally, I would draw a path like this:
1. the center of the box would be located at x and bottom and top
would be y1, y2, all in data coords
2. I would move to (x,y1) at the bottom-center of the box.
3. The x value would now need to be converted to Axes coords, possibly
by applying transData + transAxes.inverted
4. I would want to draw a line to (x-0.1, y1) where x is now in axes
coords and y is still in data coords. Then up, then right, then down,
and then close the polygon.

How do I implement this?

I must be missing something, because I still don't see why you can't do
all this very simply by using a PolyCollection, with the vertices in
axes
coordinates and the offset in data coordinates.

Eric

As I mentioned before, a blended transform would allow me to make the
moves i am interested in. However, a change of scale would change the
correspondence between data and axes coords, so the axes transform
part of the blended axes would have to be recomputed everytime the
scale changes based on where the (x,y1) point lands in the axes. Is
this correct?

Any suggestions are welcome...thanks!

Uri

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Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

--
Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.patches as mpatches
import matplotlib.transforms as mtransforms
import matplotlib.path as mpath

class MyBox(mpatches.Patch):

def __init__(self, x, w, y1, y2, **kwargs):
self.x = x
self.w = w
self.y1 = y1
self.y2 = y2
mpatches.Patch.__init__(self, **kwargs)

def get_path(self):
return mpath.Path.unit_rectangle()

def get_transform(self):

 \# Transform the data\-relative values
 box = \[\[self\.x, self\.y1\],
        \[self\.x, self\.y2\]\]
 box = self\.axes\.transData\.transform\(box\)

 \# Get the width as a fraction of the axes width
 w = self\.w \* self\.axes\.bbox\.width / 2\.0

 \# Add it to the data\-transformed coordinates
 box\[0\]\[0\] \-= w
 box\[1\]\[0\] \+= w

 return mtransforms\.BboxTransformTo\(mtransforms\.Bbox\(box\)\)

fig = plt.figure()
ax = fig.add_subplot(111)
patch = MyBox(0, 0.1, 0.5, 1.5)
ax.add_patch(patch)
ax.set_xlim((-1, 1))
ax.set_ylim((0, 2))

plt.show()

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...

------------------------------------------------------------------------------
Come build with us! The BlackBerry&reg; Developer Conference in SF, CA
is the only developer event you need to attend this year. Jumpstart your
developing skills, take BlackBerry mobile applications to market and stay
ahead of the curve. Join us from November 9&#45;12, 2009. Register now&#33;
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/matplotlib-users

--
Uri Laserson
PhD Candidate, Biomedical Engineering
Harvard Medical School (Genetics)
Massachusetts Institute of Technology (Mathematics)
phone +1 917 742 8019
laserson@...1166...