Re: [Matplotlib-users] Using an array which includes NaNs for color in streamplot

[Tony Yu <ts...@gm...>]

On Fri, Nov 16, 2012 at 11:35 AM, Jon Ramsey <jon...@gm...> wrote:

> Hi Everyone,
>
> I have just upgraded to matplotlib 1.2.0 so that I can use the streamplot
> module, which I'm quite happy about!
> However, I've noticed that when one tries to color the streamlines using a
> 2-D array which contains NaNs, streamlines of only one color are shown!  I
> have appended example code below which reproduces the problem.
>
> Meanwhile, if the following two lines are inserted inside an "if
> use_multicolor_lines:" region within streamplot.py, then the problem goes
> away (for example, after line 84 or line 115):
>     if np.any(np.isnan(color)):
>         color = np.ma.array(color, mask=np.isnan(color))
>
> This check already exists on the input arrays U and V, but not for color.
> I am also not sure this issue will persist when a normalize object is
> explicitly specified.
>
> Example code (derived from streamplot_demo.py):
>
> import numpy as np
> import matplotlib.pyplot as plt
>
> Y, X = np.mgrid[-3:3:100j, -3:3:100j]
> U = -1 - X**2 + Y
> V = 1 + X - Y**2
> speed = np.sqrt(U*U + V*V)
>
> m = np.sqrt(X**2 + Y**2) < 1.0
> speed[m] = np.nan
>
> plt.streamplot(X, Y, U, V, color=speed, linewidth=2, cmap=plt.cm.autumn)
> plt.colorbar()
> plt.show()
>
> Additional info:
> Linux 2.6.38-16-generic #67-Ubuntu SMP Thu Sep 6 17:58:38 UTC 2012 x86_64
> x86_64 x86_64 GNU/Linux
> Matplotlib v1.2.0
>
>
> Best Regards,
>
> Jon Ramsey
>
> P.S. Long time reader, first time poster.
>
>
Hi Jon,

Welcome! This fix looks good to me. Since you mentioned that you're using
the latest release, I assume you're not running matplotlib from github, so
I filed a pull request with your fix:

https://github.com/matplotlib/matplotlib/pull/1514

Thanks for the bug report and fix!
-Tony