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Re: [Matplotlib-users] defining a custom RGB colormap
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From: Michael R. <raw...@ya...> - 2011-01-06 12:43:27
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Got it now. Sorry about the confusion...by working for me I meant that set of commands ran and made the standard colorbar.
I just installed ipython (Ubuntu OS). Will try the interactive way as well. All very new. I've used PGPLOT for ~15 years.
Thanks again.
Mike
--- On Wed, 1/5/11, Paul Ivanov <piv...@gm...> wrote:
> From: Paul Ivanov <piv...@gm...>
> Subject: Re: [Matplotlib-users] defining a custom RGB colormap
> To: mat...@li...
> Date: Wednesday, January 5, 2011, 7:15 PM
> Michael Rawlins, on 2011-01-05
> 14:42, wrote:
> > Thanks for the detailed tutorial. I'm getting errors
> when I
> > attempt to use plt.subplots(1,1) and the newcm
> assignment.
> >
> > Traceback (most recent call last):
> > File "colorbar_Mytest2.py", line 17,
> in <module>
> > f, ax = plt.subplots(1,1)
> > AttributeError: 'module' object has no attribute
> 'subplots'
>
> Ah, you must be using an older version of matplotlib -
> subplots
> is a (recently added) convenience shortcut for:
>
> f = plt.figure()
> ax = plt.subplot(1,1,1)
>
> It comes in handy when you're making lots of subplots by
> letting
> you do it with one call, instead of doing that one by one
> (as I
> have rewritten below, so you could run without having to
> upgrade
> your matplotlib.
>
> > Also, what does In and Out do, as in Out[68]:
> 0.34999?
>
> That's just the prompts from IPython - I *highly* recommend
> using
> IPython in place of the default python shell for
> interactive usage.
> In[10] is what I typed, Out[10] is the result of my
> command at
> In[10].
>
> > Here are just a few of the errors I'm getting when
> executing
> > colorbar command with newcm.
>
> > Here's a simplified version that works for me:
>
> ouch! this code doesn't do quite what you want
>
> > from pylab import *
>
> Try to avoid doing this - because you will get unintended
> consequences such as the one on the following line.
>
> > vals = norm(np.linspace(14,40,1000))
>
> This was meant to go *after* you initialize the 'norm'
> variable
> with norm = mpl.colors.Normalize(...). That's the norm I
> meant to be using. But because of the "from pylab import *"
> line,
> the norm function from numpy was imported - which is what
> was being
> used on that line as written in your code.
>
> so the vals= line is equivalent to
>
> vals = numpy.norm(np.linspace(14,40,1000))
>
> which meant vals got assigned the value 886.25397758173483,
> and
> not at all what we wanted. We wanted it to get an array of
> 1000
> numbers:
>
> vals = mpl.colors.Normalize(vmin=0,
> vmax=40)(np.linspace(14,40,1000))
>
> That's where your trouble with newcm were coming from.
> Here's the
> complete example again, I've renamed the 'norm' variable
> to
> 'rawlins_norm' for clarity.
>
> import matplotlib as mpl
> import matplotlib.pyplot as plt
> from matplotlib import cm
> import numpy as np
>
> # Make a figure and axes with dimensions as desired.
> fig = plt.figure(figsize=(8,3))
> ax1 = plt.subplot(2,1,1)
> ax2 = plt.subplot(2,1,2)
>
> # Set the colormap and norm to correspond to the data for
> which
> # the colorbar will be used.
> rawlins_norm = mpl.colors.Normalize(vmin=0,
> vmax=40) # here set colorbar min/max
> # the right place for vals
> vals = rawlins_norm(np.linspace(14,40,1000))
> newcm = cm.colors.ListedColormap(cm.hot_r(vals))
>
> cb1 = mpl.colorbar.ColorbarBase(ax1, cmap=cm.hot_r,
>
>
> norm=rawlins_norm,
>
>
> orientation='horizontal')
>
> cb1.set_label('"percent"')
> cb2 = mpl.colorbar.ColorbarBase(ax2, cmap=newcm,
>
>
> orientation='horizontal')
>
> cb2.set_label("colormap interval 0.0-1.0")
> plt.subplots_adjust(hspace=.7, bottom=.2)
>
> #comment out the next line to see the original (0-40
> colormap)
> ax1.set_xlim(rawlins_norm((14,40)))
> plt.show()
>
>
> best,
> --
> Paul Ivanov
> 314 address only used for lists, off-list direct
> email at:
> http://pirsquared.org | GPG/PGP key id: 0x0F3E28F7
>
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