How to resolve line in subplot is not visible

Question

I'm trying to show speed vs velocity vs acceleration. The specific numbers don't really matter, just the concept. The last graph isn't showing a line with a slope of zero (ex: y=10). I want the program to show it with the x values of the graph being the same as the others (1 to 10). The specific numbers don't matter except for the x-values because I won't be showing the y-values. I just want a 0 slope line to be visible T-T

t = np.arange(1, 10, 1)
spd_graph = np.exp(t/2)
velo_graph = 3*t
accel_graph = .5
# plot speed
ax1 = plt.subplot(311,ylabel='Speed')
plt.plot(t, spd_graph,'c')
plt.setp(ax1.get_xticklabels(), fontsize=6)
plt.setp(ax1.get_yticklabels(), visible=False)
plt.ylim(0,30)
plt.xlim(0,10)
# plot velocity
ax2 = plt.subplot(312,ylabel='Velocity')
plt.plot(t,velo_graph,'g')
plt.setp(ax2.get_xticklabels(), fontsize=6)
plt.setp(ax2.get_yticklabels(), visible=False)
plt.ylim(0,30)
plt.xlim(0,10)
# plot acceleration
ax3 = plt.subplot(313,label='Acceleration',xlabel='Time',ylabel='Acceleration')
plt.plot(accel_graph,'b')
plt.setp(ax3.get_xticklabels(), fontsize=6)
plt.setp(ax3.get_yticklabels(), visible=False)
plt.ylim(0,30)
plt.xlim(0,10)

plt.show()

score 1 · Answer 1 · edited Nov 09 '21 at 11:48

On subplot ax3, plt.plot(accel_graph, 'b') is trying to plot a single float value, which won't work. You need to either:

make sure accel_graph is an array (or list) the same shape as t, e.g., accel_graph = 0.5*np.ones(t.shape), then plt.plot(t, accel_graph, 'b'), or something similar (e.g., plt.plot([min(t), max(t)], [0.5, 0.5], 'b')
plot a horizontal line; instead of the plt.plot(accel_graph, 'b') line, do something like ax3.axhline(0.5, color='b') (note that this will result in a horizontal line that extends beyond the minimum and maximum t values you have)

In addition, you're not correctly using the object oriented API. It should be ax1.plot(...), ax2.plot(...), ax3.plot(...), in addition to other changes.
- Also see Multiple Subplots
- How to plot in multiple subplots

t = np.arange(1, 10, 1)
spd_graph = np.exp(t/2)
velo_graph = 3*t
accel_graph = .5

fig, (ax1, ax2, ax3) = plt.subplots(3, 1, figsize=(6, 6), sharey=False)

# plot speed
ax1.plot(t, spd_graph,'c')
ax1.tick_params(axis='x', labelsize=6)
ax1.axes.yaxis.set_ticklabels([])
ax1.set(ylabel='Speed', ylim=(0, 30), xlim=(0, 10))

# plot velocity
ax2.plot(t, velo_graph,'g')
ax2.tick_params(axis='x', labelsize=6)
ax2.axes.yaxis.set_ticklabels([])
ax2.set(ylabel='Velocity', ylim=(0, 30), xlim=(0, 10))

# plot acceleration
ax3.hlines(accel_graph, t[0], t[-1])
ax3.tick_params(axis='x', labelsize=6)
ax3.axes.yaxis.set_ticklabels([])
ax3.set(xlabel='Time', ylabel='Acceleration', ylim=(0, 1), xlim=(0, 10))

plt.show()

How to resolve line in subplot is not visible

1 Answers1