[Matplotlib-users] Fwd: parametric line color

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

Oops. I meant to reply to the list.
-Tony

---------- Forwarded message ----------
From: Tony Yu <ts...@gm...>
Date: Sat, Jul 30, 2011 at 10:46 AM
Subject: Re: [Matplotlib-users] parametric line color
To: Alan G Isaac <ala...@gm...>



On Sat, Jul 30, 2011 at 12:03 AM, Alan G Isaac <ala...@gm...> wrote:

> I have many lines to plot.
> Each line has an associated parameter value.
> I'd like to pick the color for each line
> based on its parameter value by mapping
> possible parameter values to the colors
> in a color map (e.g., gist_rainbow),
> retrieving colors one at a time (based
> on the parameter value for a line).
>
> If two lines have the same parameter value,
> I need them to have exactly the same color.
>
> Hints?
>
> Thanks,
> Alan Isaac
>
>
Here's a function to do what you want. (I haven't tested it much so it could
be buggy)

Best,
-Tony

#----

import matplotlib.pyplot as plt


def make_color_manager(parameter_range, cmap='YlOrBr', start=0, stop=255):
    """Return color manager, which returns color based on parameter value.

    Parameters
    ----------
    parameter_range : 2-tuple
        minimum and maximum value of parameter
    cmap : str
        name of a matplotlib colormap (see matplotlib.pyplot.cm)
    start, stop: int
        limit colormap to this range (0 <= start < stop <= 255)
    """
    colormap = getattr(plt.cm, cmap)
    pmin, pmax = parameter_range
    def color_manager(val):
        """Return color based on parameter value `val`."""
        assert pmin <= val <= pmax
        val_norm = (val - pmin) * float(stop - start) / (pmax - pmin)
        idx = int(val_norm) + start
        return colormap(idx)
    return color_manager


if __name__ == '__main__':
    cm = make_color_manager((5, 10), start=100)
    plt.plot([0, 1], color=cm(5))
    plt.plot([0.5, 0.5], color=cm(7.5))
    plt.plot([1, 0], color=cm(10))
    plt.legend(('val = 5', 'val = 7.5', 'val = 10'))
    plt.show()