matplotlib两个传说出了情节

Question

I'm facing problem with showing two legends outside of plot. Showing multiple legends inside plot is easy - its described in matplotlib doc's with examples. Even showing one legend outside of plot is rather easy as i found here on stackoverflow (ex. here ). But i cant find working example to show two legends outside of the plot. Methods which work with one legend is not working in this case.

Here is an example. First of all base code:

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
from matplotlib.font_manager import FontProperties

fig1 = plt.figure(figsize=(17,5))
fontP = FontProperties()
fontP.set_size('small')
ax1 = fig1.add_subplot(111, aspect='equal')
ax1.grid()


# stuff for legend
rec1 = patches.Rectangle(
    (0.9, 0.25),   # (x,y)
    0.1,          # width
    0.1,          # height
    label='rectangle',
    **{
        'color': 'blue'
    }

)
ax1.add_patch(rec1)

leg = plt.legend(handles=[rec1], bbox_to_anchor=(0.7, -0.1))
fig1.savefig('sample1.png', dpi=90, bbox_inches='tight')

But now i want to draw another legend at the right side of plot. Here is the code:

...
ax1.add_patch(rec1)

l1 = plt.legend(prop=fontP, handles=[rec1], loc='center left',
                box to_anchor=(1.0, 0.5))
plt.gca().add_artist(l1)

...

And the result:

As you can see, second legend is truncated. My conclusion is that matplotlib ignores size and position of objects added with

plt.gca().add_artist(obj)

How can i fix this?

So far i found a solution but its very nasty:

Create three legends, two of them as additiontal (added by add_artist) and one as normal legend. As far matplotlib respect position and size of normal legends, move it to the right down corner and hide it with code:

leg.get_frame().set_alpha(0)

Here are the results (without setting alpha for example purpose):

It behave exactly how i want it to but as you know its nasty. Here is the final code:

import matplotlib.pyplot as plt
import matplotlib.patches as patches
from matplotlib.lines import Line2D
from matplotlib.font_manager import FontProperties

fig1 = plt.figure(figsize=(17,5))
fontP = FontProperties()
fontP.set_size('small')
ax1 = fig1.add_subplot(111, aspect='equal')
ax1.grid()

# stuff for additional legends
rec1 = patches.Rectangle(
    (0.9, 0.25),   # (x,y)
    0.1,          # width
    0.1,          # height
    label='rectangle',
    **{
        'color': 'blue'
    }
)
ax1.add_patch(rec1)

# example additional legends
l1 = plt.legend(prop=fontP, handles=[rec1], loc='center left',
bbox_to_anchor=(1.0, 0.5))
l2 = plt.legend(prop=fontP, handles=[rec1], loc=3, bbox_to_anchor=(0.4,
-0.2))

# add legends
plt.gca().add_artist(l1)
plt.gca().add_artist(l2)

# add third legend
leg = plt.legend(handles=[], bbox_to_anchor=(1.3, -0.3))
leg.get_frame().set_alpha(0) # hide legend

fig1.savefig('sample3.png', dpi=90, bbox_inches='tight')

Answer 1

I can suggest the following solution:

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec

fig = plt.figure()
fig.set_size_inches((10,10))

gs1 = gridspec.GridSpec(1, 1)
ax1 = fig.add_subplot(gs1[0])

x = np.arange(0.0, 3.0, 0.02)
y1 = np.sin(2*np.pi*x)
y2 = np.exp(-x)
l1, l2 = ax1.plot(x, y1, 'rs-', x, y2, 'go')

y3 = np.sin(4*np.pi*x)
y4 = np.exp(-2*x)
l3, l4 = ax1.plot(x, y3, 'yd-', x, y4, 'k^')

fig.legend((l1, l2), ('Line 1', 'Line 2'), "right")
fig.legend((l3, l4), ('Line 3', 'Line 4'), "lower center")

gs1.tight_layout(fig, rect=[0, 0.1, 0.8, 0.5])

I used an example from matplotlib site and followed the documentation about tight layout http://matplotlib.org/users/tight_layout_guide.html .

The result is