Re: [Matplotlib-users] Bug in colorbar()

 I am using 1.2.X and here is a minimalist example to see what happens:

Link to figure of output:
https://dl.dropbox.com/u/13534143/example.png


Example:
import numpy as np
import matplotlib as mpl
X, Y = np.meshgrid(arange(20),arange(20))
Z = np.arange(20*20)
Z = Z.reshape(20,20)
logNorm = mpl.colors.Normalize(vmin=0,vmax=200)
fig = mpl.pyplot.figure(10)
ax = fig.add_subplot(111)
surf = ax.contourf(X,Y,Z, 100, cmap=matplotlib.cm.jet, norm = logNorm)
cbar = fig.colorbar(surf, shrink=0.70, norm=logNorm)
show()
draw()

On Fri, Jul 27, 2012 at 5:00 PM, Eric Firing <ef...@ha...> wrote:

> On 2012/07/26 7:52 PM, Jeffrey Spencer wrote:
> > I am trying to make a plot with a colorbar that has a reduced axis over
> > which the colorbar is executed.
> >
> > This is set via passing in a norm to contourf:
> >          logNorm = colors.Normalize(vmax=0,vmin=-100)
> >          surf = ax.contourf(X,Y,logZ, map_scale, cmap=cm.jet,
> norm=logNorm)
> >
> > The output of this will have the colorbar extend to the full range of
> > the data and not limited by the norm set:
> >
> > cbar = fig.colorbar(surf, shrink=0.70, aspect=36, fraction=.15,pad=.03)
> >
> > so I assumed modifying by setting the norm like this would do the trick:
> >
> > cbar = fig.colorbar(surf, shrink=0.70, aspect=36, fraction=.15,pad=.03,
> > norm=logNorm)
> >
> > This isn't what happens. norm has no effect. The norm is recognized but
> > not passed to ColorbarBase is my guess from doing this instead to get
> > the desired effect:
> >
> >          axcb, _ = mpl.colorbar.make_axes_gridspec(ax, shrink=0.7)
> >          cbar = mpl.colorbar.ColorbarBase(axcb, cmap=cm.jet,
> norm=logNorm)
> >
> >
> >
> > Is this a bug or any reason why the norm is not passed through if
> > specified in colorbar??
>
> Yes, there is a reason why it is not passed through; both the cmap and
> the norm are taken from the mappable, so that the colorbar will actually
> match the mappable.  There may be a bug, but it is not immediately
> obvious to me.  Please provide a complete, minimal, self-contained
> example that illustrates the problem, and specify what version of mpl
> you are using.
>
> Eric
>
>
>
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