CODEWITHSUNDEEP
pythonmatplotlibplot
Steve
Steve

Reputation: 173

Matplotlib Reduce the Thickness of Plot Legend Line for a Pot with Two y-axes?

I have a Python3.6 code which produces two plots, one with three axis and one with two axes. The plot with three axes has a legend with thin lines.

Unfortunately the second plot legend has lines with thickness equal to the height of the label:

enter image description here

Here is the code for the second figure:

two plots on one figure

How can I reduce the thickness of the lines in the legend?

It would appear that the code didn't make it to the post.

Here it is:

#two plots on one figure

def two_scales(ax1, time, data1, data2, c1, c2):
   
    ax2 = ax1.twinx()

    ax1.plot(time, data1, 'r')
    ax1.set_xlabel("Distance ($\AA$)")
    ax1.set_ylabel('Atom Charge',color='r')

    ax2.plot(time, data2, 'b')
    ax2.set_ylabel('Orbital Energy',color='b')
    return ax1, ax2



t = data[:,0]
s1 = data[:,3]
s2 = data[:,5]

fig, ax = plt.subplots()
ax1, ax2 = two_scales(ax, t, s1, s2, 'r', 'b')


def color_y_axis(ax, color):
    for t in ax.get_yticklabels():
        t.set_color(color)
    return None
color_y_axis(ax1, 'r')
color_y_axis(ax2, 'b')

plt.title('Molecular Transforms')

patch_red = mpatches.Patch(color='red',label='Atom Charge')
patch_blue = mpatches.Patch(color='blue',label='Orbital Energy')
plt.legend(handles = [patch_red,patch_blue])

plt.draw()
plt.show()

name_plt = name+'-fig2.png'
fig.savefig(name_plt,bbox_inches='tight')

Upvotes: 0

Views: 1402

Answers (2)

ImportanceOfBeingErnest
ImportanceOfBeingErnest

Reputation: 339650

The usual way to create labels for a legend is to use the label argument of the artist to show in the legend, ax.plot(...., label="some label"). Using the actual artist, which has this label set, makes sure the legend shows a symbol wich corresponds to the artist; in case of line plot this would naturally be a line.

import matplotlib.pyplot as plt

time=[1,2,3,4]; data1=[0,5,4,3.3];data2=[100,150,89,70]

fig, ax1 = plt.subplots()
ax2 = ax1.twinx()

l1, = ax1.plot(time, data1, 'r', label='Atom Charge')
ax1.set_xlabel("Distance ($\AA$)")
ax1.set_ylabel('Atom Charge',color='r')

l2, = ax2.plot(time, data2, 'b', label='Orbital Energy')
ax2.set_ylabel('Orbital Energy',color='b')


ax1.legend(handles=[l1,l2])

plt.show()

enter image description here

Upvotes: 0

Y. Luo
Y. Luo

Reputation: 5732

Sounds like you want a line for your legend but actually used a patch. Examples and details can be found here. You can use line like this small example:

import matplotlib.lines as mlines
import matplotlib.pyplot as plt

line_red = mlines.Line2D([], [], color='red',label='Atom Charge')
line_blue = mlines.Line2D([], [], color='blue',label='Orbital Energy')
plt.legend(handles = [line_red,line_blue])
plt.show()

enter image description here

Upvotes: 1

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