python - matplotlib Legend Markers Only Once

240
votes

I often plot a point on a matplotlib plot with:

x = 10
y = 100
plot(x, y, "k*", label="Global Optimum")
legend()

However, this causes the legend to put a star in the legend twice, such that it looks like:

* * Global Optimum

when I really want it to look like:

 *  Global Optimum

How do I do this?

2
pythonmatplotlib
I wish I could upvote this question multiple times. I HATE the default numpoints=2 convention and was relieved to see someone had already taken the time to ask about it and get an answer. – Chris Redford
Mind: the option for scatterplots is scatterpoints=1 – Marcos Alex

2 Answers

254
votes

This should work:

legend(numpoints=1)

BTW, if you add the line

legend.numpoints     : 1      # the number of points in the legend line

to your matplotlibrc file, then this will be the new default.

[See also scatterpoints, depending on your plot.]

API: Link to API docs

25
votes

I like to change my matplotlib rc parameters dynamically in every python script. To achieve this goal I simply use somthing like that at the beginning of my python files.

from pylab import *
rcParams['legend.numpoints'] = 1

This will apply to all plots generated from my python file.

EDIT: For those who do not like to import pylab, the long answer is

import matplotlib as mpl
mpl.rcParams['legend.numpoints'] = 1