Re: [Matplotlib-users] using color as z-axis for plots

[Ryan M. <rm...@gm...>]

Chad Kidder wrote:
> I've got many series of data that I want to plot, and each has an  
> additional scalar that is valid for the whole series.  What I want to  
> do is plot all these series on top of each other (plot can do this  
> just fine), but with the additional scalar changing the color,  
> efectively using color as the z-axis.  I'm not seeing how to do that.   
> If there was a function where I could give a color map a value and it  
> would spit out the color, that would work, but I haven't seen it.   
> Thanks for your help.

Try using scatter instead of plot.  Specifically, the 'c' keyword argument:

       *c*:
         a color. *c* can be a single color format string, or a
         sequence of color specifications of length *N*, or a
         sequence of *N* numbers to be mapped to colors using the
         *cmap* and *norm* specified via kwargs (see below). Note
         that *c* should not be a single numeric RGB or RGBA
         sequence because that is indistinguishable from an array
         of values to be colormapped.  *c* can be a 2-D array in
         which the rows are RGB or RGBA, however.

For example:

import numpy as np
import matplotlib.pyplot as plt

x = np.random.randn(100)
y = np.random.randn(100)
data = x**2 + y**2
plt.scatter(x, y, c=data)
plt.show()

Ryan

-- 
Ryan May
Graduate Research Assistant
School of Meteorology
University of Oklahoma