Matplotlib/Pyplot: How to zoom subplots together

matplotlibzooming

I have plots of 3-axis accelerometer time-series data (t,x,y,z) in separate subplots I'd like to zoom together. That is, when I use the "Zoom to Rectangle" tool on one plot, when I release the mouse all 3 plots zoom together.

Previously, I simply plotted all 3 axes on a single plot using different colors. But this is useful only with small amounts of data: I have over 2 million data points, so the last axis plotted obscures the other two. Hence the need for separate subplots.

I know I can capture matplotlib/pyplot mouse events (http://matplotlib.sourceforge.net/users/event_handling.html), and I know I can catch other events (http://matplotlib.sourceforge.net/api/backend_bases_api.html#matplotlib.backend_bases.ResizeEvent), but I don't know how to tell what zoom has been requested on any one subplot, and how to replicate it on the other two subplots.

I suspect I have the all the pieces, and need only that one last precious clue…

-BobC

Best Answer

The easiest way to do this is by using the sharex and/or sharey keywords when creating the axes:

from matplotlib import pyplot as plt

ax1 = plt.subplot(2,1,1)
ax1.plot(...)
ax2 = plt.subplot(2,1,2, sharex=ax1)
ax2.plot(...)

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from matplotlib.pyplot import figure

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You can simply do:

import numpy as np
import matplotlib.pyplot as plt

x = np.arange(0, 7, 0.01)
    
plt.subplot(2, 1, 1)
plt.plot(x, np.sin(x))
    
plt.subplot(2, 2, 3)
plt.plot(x, np.cos(x))
    
plt.subplot(2, 2, 4)
plt.plot(x, np.sin(x)*np.cos(x))

i.e., the first plot is really a plot in the upper half (the figure is only divided into 2x1 = 2 cells), and the following two smaller plots are done in a 2x2=4 cell grid. The third argument to subplot() is the position of the plot inside the grid (in the direction of reading in English, with cell 1 being in the top-left corner): for example in the second subplot (subplot(2, 2, 3)), the axes will go to the third section of the 2x2 matrix i.e, to the bottom-left corner.

Best Answer

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