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

[Chad K. <cck...@gm...>]

On Dec 8, 2008, at 12:55 PM, Ryan May wrote:

> 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
>

Close, but not quite what I want.  Maybe this will tell what I want to  
do better:

----------------------
import numpy as n
import matplotlib.pyplot as p

nlines = 100
z = n.random.rand(nlines)
x = n.array(range(nlines))
t1, t2 = n.meshgrid(x,z)
y = t1+t2-0.5
for ii in range(nlines):
    p.plot(x,y[ii,:],color = str(z[ii]))
p.show()
-------------------
Instead of getting a grayscale plot out, I'd like to use a colormap  
like jet() or winter().  Any ideas there?





--Chad Kidder