matplotlib - How to create a heat map in python that ranges from green to red? -

i'm trying plot log ratios range -3 3 , want negative ratios green , positive red, log ratio of 0 (center) white in color. none of pre-existing color schemes in matplotlib provide option, , haven't been able figure out how output nice gradient manually.

you can create own using linearsegmentedcolormap. set red , green channels less 1.0 @ upper , lower limits colours aren't bright (here used 0.8). adjust suit taste.

see custom_cmap example on matplotlib website further details.

here's working example:

import matplotlib.pyplot plt import matplotlib.colors colors import numpy np  # dictionary defines colormap cdict = {'red':  ((0.0, 0.0, 0.0),   # no red @ 0                   (0.5, 1.0, 1.0),   # channels set 1.0 @ 0.5 create white                   (1.0, 0.8, 0.8)),  # set 0.8 not bright @ 1          'green': ((0.0, 0.8, 0.8),   # set 0.8 not bright @ 0                   (0.5, 1.0, 1.0),   # channels set 1.0 @ 0.5 create white                   (1.0, 0.0, 0.0)),  # no green @ 1          'blue':  ((0.0, 0.0, 0.0),   # no blue @ 0                   (0.5, 1.0, 1.0),   # channels set 1.0 @ 0.5 create white                   (1.0, 0.0, 0.0))   # no blue @ 1        }  # create colormap using dictionary gnrd = colors.linearsegmentedcolormap('gnrd', cdict)  # make figure , axes fig,ax = plt.subplots(1)  # fake data in range -3 3 dummydata = np.random.rand(5,5)*6.-3.  # plot fake data p=ax.pcolormesh(dummydata,cmap=gnrd,vmin=-3,vmax=3)  # make colorbar fig.colorbar(p,ax=ax)  plt.show()