using imshow with a shared x axis with matplotlib

Question

The Y limits on my imshow subplot are stuck on a seemingly arbitrary range.

In this example, I'm trying to show the mean of N trials and then plot all the N trials over time as a 2d plot.

import numpy as np
import matplotlib.pyplot as plt
np.random.seed(42)
N = 20   # number of trials
M = 3000  # number of samples in each trial
data = np.random.randn(N, M)
x = np.linspace(0,1,M)  # the M samples occur in the range 0-1 
                    # ie the sampling rate is 3000 samples per second
f, (ax1, ax2) = plt.subplots(2,1, sharex=True)
ax1.plot(x, np.mean(data, 0))
ax2.imshow(data, cmap="inferno", interpolation="nearest", extent=[0, 1, 0, N])
ax2.set_ylim(0, N)
ax1.set_ylabel("mean over trials")
ax2.set_ylabel("trial")
ax2.set_xlabel("time")

Are there any tricks to set the Y limits correctly?

Could you specify what you are trying to achieve with the second plot (e.g. detail the use of extent, why you plot data and not data.T, etc.)? — P. Camilleri
– P. Camilleri, Commented Nov 16, 2016 at 19:22

ImportanceOfBeingErnest · Accepted Answer · 2016-11-16 20:48:19Z

9

By default, imshow uses an equal aspect ratio. Since your x-axis is fixed to the extent of the plot above (ax1), which is 1, the y-axis can only extent to a fraction of 1.

The solution is actually quite simple: You just need to add

ax2.set_aspect('auto')

answered Nov 16, 2016 at 20:48

ImportanceOfBeingErnest

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