Re: [Matplotlib-users] Scatter legend with colored marker

[Jorge S. <jor...@ya...>]

Benjamin Root <ben.root@...> writes:
> 
<snip>
> Probably not directly, but I hadn't thought about that before.  For a set of 
> scatter points that are colored by values, what should the legend show?  In 
> other words, what does it *mean* for there to be a legend for points that are 
> colored in a potentially non-uniform manner?So, maybe this is desired behavior 
> (but possibly by accident)?
> Thanks for your help,
> Ben Root

I thought for a moment that legend was using the color of the first point in the
set, but a quick test reveals that no matter what colormap you specify, the
marker color inside the legend is blue. BTW, I think I've found another thing
related to legend() and scatter plots: the 'numpoints' keyword argument to
legend is not respected, as showed in the example pasted below,

Jorge

-------
import numpy as np
import matplotlib as mpl
import matplotlib.pyplot as plt

data0 = np.random.rand(10,2)
data1 = np.random.rand(10,2)
data2 = np.random.rand(10,2)
data = [data0, data1, data2]

fig, ax = plt.subplots(1,1)
norm = mpl.colors.Normalize(0,len(data))
cmap = mpl.cm.afmhot

sc = []
labels = []
for i,d in enumerate(data):
    sc.append(ax.scatter(d.T[0], d.T[1], c=np.ones(d.shape[0])*i,
            norm=norm, cmap=cmap))
    labels.append('data set ' + str(i))
ax.legend(sc, labels, numpoints=1)
plt.show()
-------