Asked By – Adam Greenhall
I’m working with data that has the data has 3 plotting parameters: x,y,c. How do you create a custom color value for a scatter plot?
Extending this example I’m trying to do:
import matplotlib import matplotlib.pyplot as plt cm = matplotlib.cm.get_cmap('RdYlBu') colors=[cm(1.*i/20) for i in range(20)] xy = range(20) plt.subplot(111) colorlist=[colors[x/2] for x in xy] #actually some other non-linear relationship plt.scatter(xy, xy, c=colorlist, s=35, vmin=0, vmax=20) plt.colorbar() plt.show()
but the result is
TypeError: You must first set_array for mappable
Now we will see solution for issue: matplotlib colorbar for scatter
From the matplotlib docs on scatter 1:
cmap is only used if c is an array of floats
So colorlist needs to be a list of floats rather than a list of tuples as you have it now.
plt.colorbar() wants a mappable object, like the CircleCollection that plt.scatter() returns.
vmin and vmax can then control the limits of your colorbar. Things outside vmin/vmax get the colors of the endpoints.
How does this work for you?
import matplotlib.pyplot as plt cm = plt.cm.get_cmap('RdYlBu') xy = range(20) z = xy sc = plt.scatter(xy, xy, c=z, vmin=0, vmax=20, s=35, cmap=cm) plt.colorbar(sc) plt.show()
This question is answered By – matt
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