Re: [Matplotlib-users] setting color and alpha channel of histograms

[John H. <jdh...@ac...>]

>>>>> "Flavio" == Flavio Codeco Coelho <fcc...@fi...> writes:

    Flavio> Hi, Is there a way to set the color of an histogram? what
    Flavio> about transparency ?

    Flavio> for example:

    Flavio> h=hist(x...  set(h,'alpha',0.75)

Of course, not all backends support the alpha channel (eg postscript),
but this is already possible with the agg backend

Here is some example code

    n, binsb, pb = hist(sb, 100,normed=True)
    set(pb, 'facecolor', 'r', 'alpha', 1.0)

Perhaps the problem with your test code above is that histogram
returns a tuple of (counts, bins, patches) and you need to set the
alpha on the patches only.

    Flavio> I would like to superimpose histograms on the same plot
    Flavio> but they would have to be of different colors and be
    Flavio> translucent.

    Flavio> I need to do this in using the matlab interface, not the
    Flavio> API.

Yep, I've done exactly this before using the code above; here's an
example image where one histogram is translucent gray superimposed
over a red histogram

http://nitace.bsd.uchicago.edu:8080/files/share/aptopower.png

JDH