matplotlib.pyplot问题与子图，np.ones和np.arange？

Question

I am plotting several data types which share the x axis so I am using the matplotlib.pylot subplots command

The shared x axis is time (in years AD). The last subplot I have is the number of independent observations as a function of the time. I have the following code

import numpy as np
import matplotlib.pyplot as plt
#
# There's a bunch of data analysis here
#
f, ax = plt.subplots(4, sharex=True)
# Here I plot the first 3 subplots with no issue
x = np.arange(900, 2000, 1)#make x array in steps of 1
ax[3].plot(x[0:28], np.ones(len(x[0:28])),'k')#one observation from 900-927 AD
ax[3].plot(x[29:62], 2*np.ones(len(x[29:62])),'k')#two observations from 928-961 AD

Now when I run this code, the subplot I get only shows the second ax[3] plot and not the first. How can I fix this?? Thanks

Answer 1

Ok, I think I found an answer. The first plot was plotting but I couldn't see it with the axes so I changed the y limits

ax[3].axes.set_ylim([0 7])

That seemed to work, although is there a way to connect these horizontal lines, perhaps with dashed lines?