Update a contour plot

Community matplotlib-users
1

Hi,
is there a way to update a contour plot? I need to display a series of
contour plots from a directory with data files and want to view them
consecutively, preferrably without building a gui for it. Is there an easy way out?

Cheers, Ralph

2

Hi Ralph,

I don't think there exists a function like the line-'set_data'-method for
collections, which are generated by 'contour'. This particular method of
lines only changes the data but leave anything else unchanged.
I attached an easy approach of updating a contour plot (simply deleting old
collections), but I'm not sure that this is the best solution.

Kind regards,
Matthias

update_contour_plot.py (589 Bytes)

···

On Monday 28 September 2009 13:52:42 Ralph Kube wrote:

Hi,
is there a way to update a contour plot? I need to display a series of
contour plots from a directory with data files and want to view them
consecutively, preferrably without building a gui for it. Is there an
easy way out?

Cheers, Ralph

3

Matthias Michler wrote:

Hi Ralph,

I don't think there exists a function like the line-'set_data'-method for collections, which are generated by 'contour'. This particular method of lines only changes the data but leave anything else unchanged.
I attached an easy approach of updating a contour plot (simply deleting old collections), but I'm not sure that this is the best solution.

I don't think you area gaining anything at all by manually deleting the collections. Better to just clear the axes, or clear the figure, and make a fresh plot.

Eric

···

Kind regards,
Matthias

On Monday 28 September 2009 13:52:42 Ralph Kube wrote:

Hi,
is there a way to update a contour plot? I need to display a series of
contour plots from a directory with data files and want to view them
consecutively, preferrably without building a gui for it. Is there an
easy way out?

Cheers, Ralph

------------------------------------------------------------------------

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4

Hi Eric,

I didn't intend to be faster or more memory saving than clearing the axes but
to preserve the properties of the axes (like the label in my example).
What are the advantages of using 'cla' instead of deleting old collections?

Kind regards,
Matthias

PS: The following works as the previous example, but using 'cla':

ax = plt.subplot(111)
for i in xrange(10):
    x = np.random.uniform(size=(20, 20)) # get some random data
    ax.contour(x)
    plt.draw() # redraw current figure
    time.sleep(1) # wait for one second
    ax.cla() # clear the axes

···

On Monday 28 September 2009 21:15:05 Eric Firing wrote:

Matthias Michler wrote:
> Hi Ralph,
>
> I don't think there exists a function like the line-'set_data'-method for
> collections, which are generated by 'contour'. This particular method of
> lines only changes the data but leave anything else unchanged.
> I attached an easy approach of updating a contour plot (simply deleting
> old collections), but I'm not sure that this is the best solution.

I don't think you area gaining anything at all by manually deleting the
collections. Better to just clear the axes, or clear the figure, and
make a fresh plot.

Eric

> Kind regards,
> Matthias
>
> On Monday 28 September 2009 13:52:42 Ralph Kube wrote:
>> Hi,
>> is there a way to update a contour plot? I need to display a series of
>> contour plots from a directory with data files and want to view them
>> consecutively, preferrably without building a gui for it. Is there an
>> easy way out?
>>
>> Cheers, Ralph

5

Hey everybody,
thank you for your answers. I use matplotlib from qt4 now. What I do is
creating a widget in a gui and using this for plotting. The plot is to
refreshed by clicking on a button. This works perfectly fine,
until I start adding a colorbar to the plot.
When I add the colorbar and replot the whole thing, the plot doesnt
fill up the area of the widget in the gui, but roughly 80% of the
horizontal extent of the last plot. So when I replot in the axes, my
plot shrinks around 20% horizontally every time I click on the button.
I found out how to delete the old colorbar, but where do I tell
matplotlib to plot into the whole extent of the plot?

This is the widget i instantiate in my gui:

class MyMplCanvas(FigureCanvas):
  def __init__(self, parent=None, width = 10, height = 12, dpi = 100, sharex = None, sharey = None):
   self.fig = Figure(figsize = (width, height), dpi=dpi, facecolor = '#FFFFFF')
  self.ax = self.fig.add_subplot(111, sharex = sharex, sharey = sharey)
  self.fig.subplots_adjust(left=0.1, bottom=0.15, right=0.9, top=0.9)
  self.xtitle="x [a.u.]"
  self.ytitle="y [a.u.]"
  self.PlotTitle = ""
  self.grid_status = True
  self.xaxis_style = 'linear'
  self.yaxis_style = 'linear'
  self.format_labels()
  self.ax.hold(False)
.......

And this would be the code I call for plotting:

  elif self.ui.radioButton_theta.isChecked() :
    data = N.vstack([ self.data_theta[self.nx/2:,:,self.filepos], self.data_theta[:self.nx/2,:,self.filepos]] )
    title_str = 'Theta T.%03d' % self.filepos

    self.ui.widget.canvas.ax.collections =
    plt = self.ui.widget.canvas.ax.contourf(data)
    self.ui.widget.canvas.fig.colorbar(plt)
    self.ui.widget.canvas.PlotTitle = title_str
    self.ui.widget.canvas.print_figure('plot')

I thought the call self.ui.widget.canvas.ax.collections = clears the axes. Any ideas?

Cheers, Ralph

Eric Firing wrote:

···

Matthias Michler wrote:

Hi Ralph,

I don't think there exists a function like the line-'set_data'-method for collections, which are generated by 'contour'. This particular method of lines only changes the data but leave anything else unchanged.
I attached an easy approach of updating a contour plot (simply deleting old collections), but I'm not sure that this is the best solution.

I don't think you area gaining anything at all by manually deleting the collections. Better to just clear the axes, or clear the figure, and make a fresh plot.

Eric

Kind regards,
Matthias

On Monday 28 September 2009 13:52:42 Ralph Kube wrote:

Hi,
is there a way to update a contour plot? I need to display a series of
contour plots from a directory with data files and want to view them
consecutively, preferrably without building a gui for it. Is there an
easy way out?

Cheers, Ralph

6

Ralph Kube wrote:

Hey everybody,
thank you for your answers. I use matplotlib from qt4 now. What I do is
creating a widget in a gui and using this for plotting. The plot is to
refreshed by clicking on a button. This works perfectly fine,
until I start adding a colorbar to the plot.
When I add the colorbar and replot the whole thing, the plot doesnt
fill up the area of the widget in the gui, but roughly 80% of the
horizontal extent of the last plot. So when I replot in the axes, my
plot shrinks around 20% horizontally every time I click on the button.
I found out how to delete the old colorbar, but where do I tell
matplotlib to plot into the whole extent of the plot?

The colorbar method or pyplot function optionally resizes the image axes and uses the liberated space to make an axes for itself. For your application, you don't want to use this option; you need to make the axes object manually and use the cax kwarg to tell colorbar to use it. Or you could generate it automatically the first time, and then reuse it for all subsequent colorbar calls.

Eric

···

This is the widget i instantiate in my gui:

class MyMplCanvas(FigureCanvas):
  def __init__(self, parent=None, width = 10, height = 12, dpi = 100, sharex = None, sharey = None):
   self.fig = Figure(figsize = (width, height), dpi=dpi, facecolor = '#FFFFFF')
  self.ax = self.fig.add_subplot(111, sharex = sharex, sharey = sharey)
  self.fig.subplots_adjust(left=0.1, bottom=0.15, right=0.9, top=0.9)
  self.xtitle="x [a.u.]"
  self.ytitle="y [a.u.]"
  self.PlotTitle = ""
  self.grid_status = True
  self.xaxis_style = 'linear'
  self.yaxis_style = 'linear'
  self.format_labels()
  self.ax.hold(False)
.......

And this would be the code I call for plotting:

  elif self.ui.radioButton_theta.isChecked() :
    data = N.vstack([ self.data_theta[self.nx/2:,:,self.filepos], self.data_theta[:self.nx/2,:,self.filepos]] )
    title_str = 'Theta T.%03d' % self.filepos

    self.ui.widget.canvas.ax.collections =
    plt = self.ui.widget.canvas.ax.contourf(data)
    self.ui.widget.canvas.fig.colorbar(plt)
    self.ui.widget.canvas.PlotTitle = title_str
    self.ui.widget.canvas.print_figure('plot')

I thought the call self.ui.widget.canvas.ax.collections = clears the axes. Any ideas?

Cheers, Ralph

Eric Firing wrote:

Matthias Michler wrote:

Hi Ralph,

I don't think there exists a function like the line-'set_data'-method for collections, which are generated by 'contour'. This particular method of lines only changes the data but leave anything else unchanged.
I attached an easy approach of updating a contour plot (simply deleting old collections), but I'm not sure that this is the best solution.

I don't think you area gaining anything at all by manually deleting the collections. Better to just clear the axes, or clear the figure, and make a fresh plot.

Eric

Kind regards,
Matthias

On Monday 28 September 2009 13:52:42 Ralph Kube wrote:

Hi,
is there a way to update a contour plot? I need to display a series of
contour plots from a directory with data files and want to view them
consecutively, preferrably without building a gui for it. Is there an
easy way out?

Cheers, Ralph

------------------------------------------------------------------------------
Come build with us! The BlackBerry® 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 9-12, 2009. Register now!
http://p.sf.net/sfu/devconf
_______________________________________________
Matplotlib-users mailing list
Matplotlib-users@lists.sourceforge.net
matplotlib-users List Signup and Options

7

Hey Eric,

The colorbar method or pyplot function optionally resizes the image axes and uses the liberated space to make an axes for itself. For your application, you don't want to use this option; you need to make the axes object manually and use the cax kwarg to tell colorbar to use it. Or you could generate it automatically the first time, and then reuse it for all subsequent colorbar calls.

this is exactly what I worked out :wink:
I create the first colorbar and save the axis object it plots itself in:

  self.colorbar = self.ui.widget.canvas.fig.colorbar(plt, ax = self.ui.widget.canvas.ax.get_axes())

Then I plot each new colorbar into that axes object by specifying the cax keyword via
  self.ui.widget.canvas.fig.colorbar(plt, cax = self.colorbar.ax)

Thank you for your help.
Cheers, Ralph