Embedding small plots inside subplots in matplotlib

61
votes

If you want to insert a small plot inside a bigger one you can use Axes, like here.

The problem is that I don't know how to do the same inside a subplot.

I have several subplots and I would like to plot a small plot inside each subplot. The example code would be something like this:

import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure()

for i in range(4):
    ax = fig.add_subplot(2,2,i)
    ax.plot(np.arange(11),np.arange(11),'b')

    #b = ax.axes([0.7,0.7,0.2,0.2]) 
    #it gives an error, AxesSubplot is not callable

    #b = plt.axes([0.7,0.7,0.2,0.2])
    #plt.plot(np.arange(3),np.arange(3)+11,'g')
    #it plots the small plot in the selected position of the whole figure, not inside the subplot

Any ideas?

Thanks in advance!

4
matplotlibplotembeddingaxessubplot
See this related post - wflynny
Working on the solution, I found another problem... stackoverflow.com/questions/17478165/… - Pablo
Thank you very much to both of you. I could do what I was looking for with zoomed_inset_axis from AxesGrid as Bill suggested, and also with Pablo's function. Finally I'm using Pablo's function as it is more confortable than the AxesGrid to plot all the small figures with the same size in all subplots. Thanks again! - Argitzen

4 Answers

62
votes

I wrote a function very similar to plt.axes. You could use it for plotting yours sub-subplots. There is an example...

import matplotlib.pyplot as plt
import numpy as np

def add_subplot_axes(ax,rect,axisbg='w'):
    fig = plt.gcf()
    box = ax.get_position()
    width = box.width
    height = box.height
    inax_position  = ax.transAxes.transform(rect[0:2])
    transFigure = fig.transFigure.inverted()
    infig_position = transFigure.transform(inax_position)    
    x = infig_position[0]
    y = infig_position[1]
    width *= rect[2]
    height *= rect[3]  # <= Typo was here
    subax = fig.add_axes([x,y,width,height],axisbg=axisbg)
    x_labelsize = subax.get_xticklabels()[0].get_size()
    y_labelsize = subax.get_yticklabels()[0].get_size()
    x_labelsize *= rect[2]**0.5
    y_labelsize *= rect[3]**0.5
    subax.xaxis.set_tick_params(labelsize=x_labelsize)
    subax.yaxis.set_tick_params(labelsize=y_labelsize)
    return subax

def example1():
    fig = plt.figure(figsize=(10,10))
    ax = fig.add_subplot(111)
    rect = [0.2,0.2,0.7,0.7]
    ax1 = add_subplot_axes(ax,rect)
    ax2 = add_subplot_axes(ax1,rect)
    ax3 = add_subplot_axes(ax2,rect)
    plt.show()

def example2():
    fig = plt.figure(figsize=(10,10))
    axes = []
    subpos = [0.2,0.6,0.3,0.3]
    x = np.linspace(-np.pi,np.pi)
    for i in range(4):
        axes.append(fig.add_subplot(2,2,i))
    for axis in axes:
        axis.set_xlim(-np.pi,np.pi)
        axis.set_ylim(-1,3)
        axis.plot(x,np.sin(x))
        subax1 = add_subplot_axes(axis,subpos)
        subax2 = add_subplot_axes(subax1,subpos)
        subax1.plot(x,np.sin(x))
        subax2.plot(x,np.sin(x))
if __name__ == '__main__':
    example2()
    plt.show()

enter image description here

56
votes

You can now do this with matplotlibs inset_axes method (see docs):

from mpl_toolkits.axes_grid.inset_locator import inset_axes
inset_axes = inset_axes(parent_axes,
                    width="30%", # width = 30% of parent_bbox
                    height=1., # height : 1 inch
                    loc=3)

Update: As Kuti pointed out, for matplotlib version 2.1 or above, you should change the import statement to:

from mpl_toolkits.axes_grid1.inset_locator import inset_axes

There is now also a full example showing all different options available.

17
votes

From matplotlib 3.0 on, you can use matplotlib.axes.Axes.inset_axes:

import numpy as np
import matplotlib.pyplot as plt

fig, axes = plt.subplots(2,2)

for ax in axes.flat:
    ax.plot(np.arange(11),np.arange(11))

    ins = ax.inset_axes([0.7,0.7,0.2,0.2])

plt.show()

enter image description here

The difference to mpl_toolkits.axes_grid.inset_locator.inset_axes mentionned in @jrieke's answer is that this is a lot easier to use (no extra imports etc.), but has the drawback of being slightly less flexible (no argument for padding or corner locations).

16
votes

source: https://matplotlib.org/examples/pylab_examples/axes_demo.html

enter image description here 

from mpl_toolkits.axes_grid.inset_locator import inset_axes
import matplotlib.pyplot as plt
import numpy as np

# create some data to use for the plot
dt = 0.001
t = np.arange(0.0, 10.0, dt)
r = np.exp(-t[:1000]/0.05)               # impulse response
x = np.random.randn(len(t))
s = np.convolve(x, r)[:len(x)]*dt  # colored noise

fig = plt.figure(figsize=(9, 4),facecolor='white')
ax = fig.add_subplot(121)
# the main axes is subplot(111) by default
plt.plot(t, s)
plt.axis([0, 1, 1.1*np.amin(s), 2*np.amax(s)])
plt.xlabel('time (s)')
plt.ylabel('current (nA)')
plt.title('Subplot 1: \n Gaussian colored noise')

# this is an inset axes over the main axes
inset_axes = inset_axes(ax, 
                    width="50%", # width = 30% of parent_bbox
                    height=1.0, # height : 1 inch
                    loc=1)
n, bins, patches = plt.hist(s, 400, normed=1)
#plt.title('Probability')
plt.xticks([])
plt.yticks([])

ax = fig.add_subplot(122)
# the main axes is subplot(111) by default
plt.plot(t, s)
plt.axis([0, 1, 1.1*np.amin(s), 2*np.amax(s)])
plt.xlabel('time (s)')
plt.ylabel('current (nA)')
plt.title('Subplot 2: \n Gaussian colored noise')

plt.tight_layout()
plt.show()