Setting the Subplot Axis Range

When visualizing data using subplots, it is often necessary to adjust the axis range to enhance readability. This article addresses the question of how to set the y-axis range of a specific subplot.

In the example provided, the FFT plot contains an overly large spike that obscures the underlying data. To rectify this, we need to restrict the y-axis range to a sensible interval.

The attempted code:

pylab.ylim([0,1000])

fails because the statement is executed before the subplot is created. The correct placement is after the pylab.plot() command.

pylab.subplot(h,w,2)
pylab.title("FFT")
fft = scipy.fft(rawsignal)
pylab.plot(abs(fft))
pylab.ylim([0,1000])

Additionally, since the use of pylab is now deprecated by Matplotlib, it is recommended to use the pyplot interface instead:

import matplotlib.pyplot as plt

# Set the y-axis range for the second subplot
plt.subplot(h, w, 2)
plt.title("FFT")
fft = scipy.fft(rawsignal)
plt.plot(abs(fft))
plt.ylim([0, 1000])

By following these recommendations, you can effectively set the axis range for your subplots and improve the visualization of your data.