CODEWITHSUNDEEP
pythonmatplotlib
SAkht312
SAkht312

Reputation: 55

Showing legend for only one subplot using matplotlib

I'm facing a problem in showing the legend in the correct format using matplotlib.

EDIT: I have 4 subplots in a figure in 2 by 2 format and I want legend only on the first subplot which has two lines plotted on it. The legend that I got using the code attached below contained endless entries and extended vertically throughout the figure. When I use the same code using linspace to generate fake data the legend works absolutely fine. 

import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as mtick
import os

#------------------set default directory, import data and create column output vectors---------------------------#

path="C:/Users/Pacman/Data files"
os.chdir(path)
data =np.genfromtxt('vrp.txt')

x=np.array([data[:,][:,0]])

y1=np.array([data[:,][:,6]])
y2=np.array([data[:,][:,7]])
y3=np.array([data[:,][:,9]])
y4=np.array([data[:,][:,11]])
y5=np.array([data[:,][:,10]])

nrows=2
ncols=2
tick_l=6   #length of ticks
fs_axis=16 #font size of axis labels


plt.rcParams['axes.linewidth'] = 2         #Sets global line width of all the axis
plt.rcParams['xtick.labelsize']=14         #Sets global font size for x-axis labels
plt.rcParams['ytick.labelsize']=14         #Sets global font size for y-axis labels



plt.subplot(nrows, ncols, 1)

ax=plt.subplot(nrows, ncols, 1)
l1=plt.plot(x, y2, 'yo',label='Flow rate-fan')
l2=plt.plot(x,y3,'ro',label='Flow rate-discharge')
plt.title('(a)')
plt.ylabel('Flow rate ($m^3 s^{-1}$)',fontsize=fs_axis)
plt.xlabel('Rupture Position (ft)',fontsize=fs_axis)

# This part is not working
plt.legend(loc='upper right', fontsize='x-large')

#Same code for rest of the subplots

I tried to implement a fix suggested in the following link, however, could not make it work: how do I make a single legend for many subplots with matplotlib?

Any help in this regard will be highly appreciated.

Upvotes: 2

Views: 3998

Answers (2)

Joseph
Joseph

Reputation: 71

If I understand correctly, you need to tell plt.legend what to put as legends... at this point it is being loaded empty. What you get must be from another source. I have quickly the following, and of course when I run fig.legend as you do I get nothing. 

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()
ax1 = fig.add_axes([0.1, 0.1, 0.4, 0.7])
ax2 = fig.add_axes([0.55, 0.1, 0.4, 0.7])

x = np.arange(0.0, 2.0, 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 = ax2.plot(x, y3, 'yd-', x, y4, 'k^')

fig.legend(loc='upper right', fontsize='x-large')

#fig.legend((l1, l2), ('Line 1', 'Line 2'), 'upper left')
#fig.legend((l3, l4), ('Line 3', 'Line 4'), 'upper right')
plt.show()

I'd suggest doing one by one, and then applying for all.

Upvotes: 1

Sajjan Singh
Sajjan Singh

Reputation: 2553

It is useful to work with the axes directly (ax in your case) when when working with subplots. So if you set up two plots in a figure and only wish to have a legend in your second plot:

t = np.linspace(0, 10, 100)

plt.figure()

ax1 = plt.subplot(2, 1, 1)
ax1.plot(t, t * t)

ax2 = plt.subplot(2, 1, 2)
ax2.plot(t, t * t * t)
ax2.legend('Cubic Function')

Note that when creating the legend, I am doing so on ax2 as opposed to plt. If you wish to create a second legend for the first subplot, you can do so in the same way but on ax1.

Upvotes: 0

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