1 colorbar on 2 subplots.

Community matplotlib-users
1

Hi,
I am trying to put 1 colorbar on 2 subplots, but failing miserably.

I have tried multiple approaches, involving subplot2grid, add_axes, AxesGrid etc.

If anyone has a “canned” routine or knows what to do, your help is greatly appreciated.

Here is my code block:

fig = pyplot.figure()

ax1 = pyplot.subplot2grid((2,2),(0,0))
cx1  = pyplot.contourf(x,y,var1,var_cint,origin='lower',extend='both')

ax2 = pyplot.subplot2grid((2,2),(0,1))
cx2  = pyplot.contourf(x,y,var2,var_cint,origin='lower',extend='both')

Now I want to put 1 colorbar to these subplots.

Thanks!

2

This example seems to be a very simple example of what you want:

http://matplotlib.sourceforge.net/examples/pylab_examples/subplots_adjust.html

Basically, you need to create an axes specifically for the colorbar (e.g. colorbar_ax) and call pyplot.colorbar(cax=colorbar_ax); or you can let mpl automatically take space from one of your existing axes: for example, pyplot.colorbar(ax=ax2).

You can also pass a mappable to pyplot.colorbar (in your example, cx1 or cx2), but by default, it will grab the most recently created one. Note, using the single colorbar for both subplots only makes sense if var_cint (in your code) is defining the values of the contour levels (as opposed to the number of contour levels). Otherwise, the colorbar will only be accurate for one of the two plots.

HTH,
-Tony

···

On Fri, Nov 4, 2011 at 4:49 PM, Rahul Mahajan <aerorahul@…287…> wrote:

Hi,
I am trying to put 1 colorbar on 2 subplots, but failing miserably.

I have tried multiple approaches, involving subplot2grid, add_axes, AxesGrid etc.

If anyone has a “canned” routine or knows what to do, your help is greatly appreciated.

Here is my code block:

fig = pyplot.figure()

ax1 = pyplot.subplot2grid((2,2),(0,0))
cx1  = pyplot.contourf(x,y,var1,var_cint,origin='lower',extend='both')

ax2 = pyplot.subplot2grid((2,2),(0,1))




cx2  = pyplot.contourf(x,y,var2,var_cint,origin='lower',extend='both')

Now I want to put 1 colorbar to these subplots.

3

Even easier is to use the axes_grid1 module and create an AxesGrid object. In the constructor, you can specify the colorbar mode as ‘single’. Then, the AxesGrid object has the axes for plots, and a separate list for any axes for use for colobars.

Does that help?
Ben Root

···

On Friday, November 4, 2011, Tony Yu <tsyu80@…287…> wrote:

On Fri, Nov 4, 2011 at 4:49 PM, Rahul Mahajan <aerorahul@…287…> wrote:

Hi,
I am trying to put 1 colorbar on 2 subplots, but failing miserably.

I have tried multiple approaches, involving subplot2grid, add_axes, AxesGrid etc.

If anyone has a “canned” routine or knows what to do, your help is greatly appreciated.

Here is my code block:

fig = pyplot.figure()

ax1 = pyplot.subplot2grid((2,2),(0,0))

cx1  = pyplot.contourf(x,y,var1,var_cint,origin='lower',extend='both')

ax2 = pyplot.subplot2grid((2,2),(0,1))
cx2  = pyplot.contourf(x,y,var2,var_cint,origin='lower',extend='both')

Now I want to put 1 colorbar to these subplots.

This example seems to be a very simple example of what you want:
http://matplotlib.sourceforge.net/examples/pylab_examples/subplots_adjust.html

Basically, you need to create an axes specifically for the colorbar (e.g. colorbar_ax) and call pyplot.colorbar(cax=colorbar_ax); or you can let mpl automatically take space from one of your existing axes: for example, pyplot.colorbar(ax=ax2).

You can also pass a mappable to pyplot.colorbar (in your example, cx1 or cx2), but by default, it will grab the most recently created one. Note, using the single colorbar for both subplots only makes sense if var_cint (in your code) is defining the values of the contour levels (as opposed to the number of contour levels). Otherwise, the colorbar will only be accurate for one of the two plots.

HTH,
-Tony