xlabel vertical positioning

Community matplotlib-users
1

Hi,

This is probably a simple question, but what is the best way to control the vertical positioning of the x-axis label? I tried:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as mpl

fig = mpl.figure()
ax = fig.add_subplot(111)
ax.set_xlabel("Hello",position=(0.5,-0.2))
fig.savefig('test.png')

But this doesn't work. Strangely, changing the first position element does shift the label left and right, but changing the second does not move the label vertically.

I'm using matplotlib 0.98.5.2

Thanks for any advice!

Thomas

2

You can use 'LABELPAD' to adjust label position.
e.g.

import pylab
hAxes = pylab.axes()
pylab.xlabel('test')
hAxes.xaxis.LABELPAD = 0
pylab.show()

···

--
Yong-Duk Jin

On Tuesday 28 April 2009 14:08:50 Thomas Robitaille wrote:

Hi,

This is probably a simple question, but what is the best way to
control the vertical positioning of the x-axis label? I tried:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as mpl

fig = mpl.figure()
ax = fig.add_subplot(111)
ax.set_xlabel("Hello",position=(0.5,-0.2))
fig.savefig('test.png')

But this doesn't work. Strangely, changing the first position element
does shift the label left and right, but changing the second does not
move the label vertically.

I'm using matplotlib 0.98.5.2

Thanks for any advice!

Thomas

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3

Thanks! I could not find any documentation relating to this, so I was wondering whether it would be better to go with a well-documented function such as text or figtext? What would be best to use?

Thomas

···

On 28 Apr 2009, at 22:27, Yong-Duk Jin wrote:

You can use 'LABELPAD' to adjust label position.
e.g.

import pylab
hAxes = pylab.axes()
pylab.xlabel('test')
hAxes.xaxis.LABELPAD = 0
pylab.show()

--
Yong-Duk Jin

On Tuesday 28 April 2009 14:08:50 Thomas Robitaille wrote:

Hi,

This is probably a simple question, but what is the best way to
control the vertical positioning of the x-axis label? I tried:

import matplotlib
matplotlib.use('Agg')
import matplotlib.pyplot as mpl

fig = mpl.figure()
ax = fig.add_subplot(111)
ax.set_xlabel("Hello",position=(0.5,-0.2))
fig.savefig('test.png')

But this doesn't work. Strangely, changing the first position element
does shift the label left and right, but changing the second does not
move the label vertically.

I'm using matplotlib 0.98.5.2

Thanks for any advice!

Thomas

---------------------------------------------------------------------------
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Conference from O'Reilly Media. Velocity features a full day of
expert-led, hands-on workshops and two days of sessions from industry
leaders in dedicated Performance & Operations tracks. Use code vel09scf
and Save an extra 15% before 5/3. http://p.sf.net/sfu/velocityconf
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Conference from O'Reilly Media. Velocity features a full day of
expert-led, hands-on workshops and two days of sessions from industry
leaders in dedicated Performance & Operations tracks. Use code vel09scf
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4

There’s now a documented way to do this in SVN HEAD, by passing labelpad as an argument to the xlabel/ylabel functions.

Ryan

···

On Tue, Apr 28, 2009 at 9:54 PM, Thomas Robitaille <thomas.robitaille@…287…> wrote:

Thanks! I could not find any documentation relating to this, so I was

wondering whether it would be better to go with a well-documented

function such as text or figtext? What would be best to use?

Thomas

On 28 Apr 2009, at 22:27, Yong-Duk Jin wrote:

You can use ‘LABELPAD’ to adjust label position.

e.g.

import pylab

hAxes = pylab.axes()

pylab.xlabel(‘test’)

hAxes.xaxis.LABELPAD = 0

pylab.show()

–
Ryan May
Graduate Research Assistant

School of Meteorology
University of Oklahoma
Sent from Norman, Oklahoma, United States

5

Ryan May wrote:

    Thanks! I could not find any documentation relating to this, so I was
    wondering whether it would be better to go with a well-documented
    function such as text or figtext? What would be best to use?

    Thomas

     > You can use 'LABELPAD' to adjust label position.
     > e.g.
     >
     > import pylab
     > hAxes = pylab.axes()
     > pylab.xlabel('test')
     > hAxes.xaxis.LABELPAD = 0
     > pylab.show()
     >

There's now a documented way to do this in SVN HEAD, by passing labelpad as an argument to the xlabel/ylabel functions.

Ryan,

Good idea, thanks.

Quick thought, with no investigation on my part: wouldn't it be more natural and more useful if text placement pads like this were in font-size units, like the "em" and "ex", so that they would scale with the font size? I think that this would make the need to set them manually much less common.

Eric

···

On Tue, Apr 28, 2009 at 9:54 PM, Thomas Robitaille > <thomas.robitaille@...287... <mailto:thomas.robitaille@…287…>> wrote:
    On 28 Apr 2009, at 22:27, Yong-Duk Jin wrote:

Ryan

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma
Sent from Norman, Oklahoma, United States

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6

Good idea, I agree that might help. I was just going for somewhat of a quick hack, by just cleaning up access to a pre-existing constant. Right now it adds this pad value scaled by dpi/72.0 to an appropriate start in pixels. Any idea how the math could include a font size?

Ryan

···

On Thu, May 7, 2009 at 3:13 PM, Eric Firing <efiring@…202…> wrote:

Ryan May wrote:

On Tue, Apr 28, 2009 at 9:54 PM, Thomas Robitaille <thomas.robitaille@…287… mailto:thomas.robitaille@...287...> wrote:

Thanks! I could not find any documentation relating to this, so I was

wondering whether it would be better to go with a well-documented

function such as text or figtext? What would be best to use?



Thomas



On 28 Apr 2009, at 22:27, Yong-Duk Jin wrote:



 > You can use 'LABELPAD' to adjust label position.

 > e.g.

 >

 > import pylab

 > hAxes = pylab.axes()

 > pylab.xlabel('test')

 > hAxes.xaxis.LABELPAD = 0

 > pylab.show()

 >

There’s now a documented way to do this in SVN HEAD, by passing labelpad as an argument to the xlabel/ylabel functions.

Ryan,

Good idea, thanks.

Quick thought, with no investigation on my part: wouldn’t it be more natural and more useful if text placement pads like this were in font-size units, like the “em” and “ex”, so that they would scale with the font size? I think that this would make the need to set them manually much less common.

–
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma
Sent from Norman, Oklahoma, United States

7

Ryan May wrote:

    Ryan May wrote:

           Thanks! I could not find any documentation relating to this,
        so I was
           wondering whether it would be better to go with a well-documented
           function such as text or figtext? What would be best to use?

           Thomas

            > You can use 'LABELPAD' to adjust label position.
            > e.g.
            >
            > import pylab
            > hAxes = pylab.axes()
            > pylab.xlabel('test')
            > hAxes.xaxis.LABELPAD = 0
            > pylab.show()
            >

        There's now a documented way to do this in SVN HEAD, by passing
        labelpad as an argument to the xlabel/ylabel functions.

    Ryan,

    Good idea, thanks.

    Quick thought, with no investigation on my part: wouldn't it be more
    natural and more useful if text placement pads like this were in
    font-size units, like the "em" and "ex", so that they would scale
    with the font size? I think that this would make the need to set
    them manually much less common.

Good idea, I agree that might help. I was just going for somewhat of a quick hack, by just cleaning up access to a pre-existing constant. Right now it adds this pad value scaled by dpi/72.0 to an appropriate start in pixels. Any idea how the math could include a font size?

In any case where the text object exists at the time the calculation is needed, and the method doing the calculation has access to that object, it is just a matter of changing, for example,

             self.label.set_position( (x, bottom - self.labelpad*self.figure.dpi / 72.0))

to

             pad = (self.labelpad_rel * self.label.get_size() * self.figure.dpi / 72.0)
             self.label.set_position( (x, bottom - pad))

I think that most of the pads used in mpl are associated with text objects in such a way that this can be done. The question then becomes one of how to implement it in a way that doesn't wreck existing code, and doesn't create intolerable clutter. If this can be done, I think it would make a *significant* improvement in mpl usability--at least for anyone who needs to rescale plots for publication or for presentation display, for example.

Another thing to watch out for in trying to make such a change: the pad calculation would need to be done late enough to reflect the font size at draw-time. I have not looked to see whether this is already the case, or whether it would require substantial refactoring.

I was not suggesting that your labelpad patch should be changed right away, but rather using it as an opportunity to raise the larger design question, and see whether anyone is interested in pursuing it.

I have raised questions about pad units before, and in fact we now have legend.borderpad (in legend font units) that replaces legend.pad (in normalized axes units).

Eric

···

On Thu, May 7, 2009 at 3:13 PM, Eric Firing <efiring@...202... > <mailto:efiring@…202…>> wrote:
        On Tue, Apr 28, 2009 at 9:54 PM, Thomas Robitaille > <thomas.robitaille@...287... > <mailto:thomas.robitaille@…287…> > <mailto:thomas.robitaille@…287… > <mailto:thomas.robitaille@…287…>>> wrote:
           On 28 Apr 2009, at 22:27, Yong-Duk Jin wrote:

Ryan

--
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma
Sent from Norman, Oklahoma, United States