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Re: [Matplotlib-users] Selecting a color from a given color map. Tony Yu Thu Feb 16 14:01:13 2012

On Thu, Feb 16, 2012 at 4:14 PM, Daniel Welling <[EMAIL PROTECTED]>wrote:

> Greetings.
>
> I have a series of lines that I would like to plot on the same axis,
> but I would like to set the color of each such that the range of
> colors used progresses through a given color map (e.g. the default Jet
> map.)  For example, if I have 7 lines, the first would use the first
> most color from the Jet color map (blue.)  The next line would use the
> color that is 1/7 the way up the map, e.g. green or so.  This would
> continue until the last line was red.
>
> How would I go about doing this (that is, loading a color map and
> pulling a specific color from it that could be handed to plot as an
> rgba tuple)?
>
> Thanks!
> -dw
>
>
Hi Daniel,

You can just pass values to a colormap. If those values are evenly spaced
between 0 and 1, you'll get the result you desire. Example:

#~~~~~

import numpy as np
import matplotlib.pyplot as plt

n_lines = 10
x = np.linspace(0, 10)

phase_shift = np.linspace(0, np.pi, n_lines)
color_idx = np.linspace(0, 1, n_lines)
for i, shift in zip(color_idx, phase_shift):
    plt.plot(x, np.sin(x - shift), color=plt.cm.jet(i))

plt.show()

#~~~~~

Coincidentally, this past weekend, I started wrapping up random code like
this into a utility package. See `cycle_cmap` in this package:
https://github.com/tonysyu/mpltools/blob/master/mpltools/color.py. The
package is still in the early stages, and function names could easily
change, so use with caution.

Best,
-Tony
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