matplotlib legend: Including markers and lines from two different graphs in one line

问题

I've been doing some linear regression and want to plot the markers (original data) and the lines (regression) on the same line in the legend. For simplicity, here's a fake regression:

from pylab import *
ax = subplot(1,1,1)
p1, = ax.plot([1,2,3,4,5,6],'r-', label="line 1")
p2, = ax.plot([6,5,4,3,2,1],'b-', label="line 2")

p3, = ax.plot([1.2,1.8,3.1,4.1,4.8,5.9],'ro', label="dots 1")
p4, = ax.plot([6.1,5.1,3.8,3.1,1.9,0.9],'bo', label="dots 2")

ax.legend(loc='center right',numpoints=1)
show()

So I want the legend to consist of 2 lines, each showing a line and a dot, instead of 4 lines. How can I do that?

回答1:

You just need to use legend a bit more directly. See Matplotlib - How to make the marker face color transparent without making the line transparent and user guide.

ax.legend([(p1, p3), (p2, p4)], ['set 1', 'set 2'])
plt.draw()

回答2:

You can just try with

from pylab import *
ax = subplot(1,1,1)
p1, = ax.plot([1,2,3,4,5,6],'r-')
p2, = ax.plot([6,5,4,3,2,1],'b-')

p3, = ax.plot([1.2,1.8,3.1,4.1,4.8,5.9],'r-o', label="dots 1")
p4, = ax.plot([6.1,5.1,3.8,3.1,1.9,0.9],'b-o', label="dots 2")

ax.legend(loc='center right',numpoints=1)
show()

or if you want a poor man's solution, you can plot something outside your plotting range and label only that plot. For instance

p5 = ax.plot(ones(2)*1e6,ones(2)*1e6,'r-o', label="dots 1")

do the same for the other label and then force your plot not to include p5, for example, like this

ax.set_xlim(0,10);ax.set_ylim(0,10)

回答3:

I usually solve this problem by creating dummy lines with the plot properties that I am interested in showing. However, I think @tcaswell's solution is better.

from matplotlib.lines import Line2D

def create_dummy_line(**kwds):
    return Line2D([], [], **kwds)

# your code here

# Create the legend
lines = [
    ('name A', {'color': 'red', 'linestyle': '-', 'marker': 'o'}),
    ('name B', {'color': 'blue', 'linestyle': '-', 'marker': 'o'}),
]
ax.legend(
    # Line handles
    [create_dummy_line(**l[1]) for l in lines],
    # Line titles
    [l[0] for l in lines],
    loc='center right'
)

来源：https://stackoverflow.com/questions/21624818/matplotlib-legend-including-markers-and-lines-from-two-different-graphs-in-one

标签

python

matplotlib

legend