Matplotlib normalize colorbar (Python)

Question

I'm trying to plot a contourf-plot using matplotlib (and numpy of course). And it works, it plots what it should plot, but unfortunatelly I cannot set the colorbar range. The problem is that I have a plenty of plots and need all of them to have the same colorbar (same min and max, same colors). I copy&past-ed almost every code snippet I found on the internet, but without success. My code so far:

    import numpy as np;
    import matplotlib as mpl;
    import matplotlib.pyplot as plt;
    [...]
    plotFreq, plotCoord = np.meshgrid(plotFreqVect, plotCoordVect);

    figHandler = plt.figure();
    cont_PSD = plt.contourf(plotFreq, plotCoord, plotPxx, 200, linestyle=None);


    normi = mpl.colors.Normalize(vmin=-80, vmax=20);

    colbar_PSD = plt.colorbar(cont_PSD);
    colbar_PSD.set_norm(normi);
    #colbar_PSD.norm = normi;
    #mpl.colors.Normalize(vmin=-80, vmax=20);

    plt.axis([1, 1000, -400, 400]);

As you can see there are three different lines for the colorbar norm, none of them is working. The range is still set automatically... I mean everything else is working, why not the colorbar? I don't even get errors or warnings.

Thanks, itpdg

EDIT 1: Pictures, with plt.clim(-80,20):

Answer 1

Please user the levels parameter, a set of examples:

In [9]:

ndom
z = np.random.random((10,10))

Without levels, colorbar will be auto-scaled

In [11]:
plt.contourf(z)
plt.colorbar()
Out[11]:
<matplotlib.colorbar.Colorbar at 0x120d47390>

In [12]:
plt.contourf(z*2)
plt.colorbar()
Out[12]:
<matplotlib.colorbar.Colorbar at 0x120f6ac10>

Control colorbar with explicit levels

In [13]:
plt.contourf(z*2, levels=np.linspace(0,2,20))
plt.colorbar()
Out[13]:
<matplotlib.colorbar.Colorbar at 0x121b119d0>

In [14]:
plt.contourf(z, levels=np.linspace(0,2,20))
plt.colorbar()
Out[14]:
<matplotlib.colorbar.Colorbar at 0x120dc3510>