问题
I have an errorbar plot where the xaxis is a list of datetime objects. The standard plotting method will put the first and last point so that they are right on the bounding box of the plot. I would like to offset by a half tick so that the first and last point can be seen clearly.
ax.axis(xmin=-0.5,xmax=len(dates)-0.5)
does not work for obvious reasons. It would be nice to be able to do this without hardcoding any dates.
The following will produce a plot which has ten points but you can really only see 8.
import datetime
import matplotlib.pyplot as plt
dates = [datetime.date(2002, 3, 11) - datetime.timedelta(days=x) for x in range(0, 10)]
yvalues = [2, 4, 1,7,9,2, 4, 1,7,9]
errorvalues = [0.4, 0.1, 0.3,0.4, 0.1,.4, 0.1, 0.3,0.4, 0.1]
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.errorbar(dates,yvalues,yerr=errorvalues,fmt='.')
fig.autofmt_xdate()
plt.show()
回答1:
An ugly fix for this could be the following
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.errorbar(range(len(dates)),yvalues,yerr=errorvalues)
ax.set_xticks(range(len(dates))
ax.set_xticklabels(dates, fontsize=8)
ax.axis(xmin=-0.5,xmax=len(dates)-0.5)
fig.autofmt_xdate()
The downside to this is that the axis objects are not of the datetime type so you can't use many functions.
回答2:
You can use ax.margins to get what you want.
Without seeing your data, it's hard to know how big of a margin you actually want. If you're plotting with python datetime-types, a margin of 1 corresponds to a pretty big margin:
fig, ax = plt.subplots()
ax.bar(x, y)
[t.set_ha('right') for t in ax.get_xticklabels()]
[t.set_rotation_mode('anchor') for t in ax.get_xticklabels()]
[t.set_rotation(45) for t in ax.get_xticklabels()]
ax.margins(x=1)
But again, it's hard to get too specific without seeing your existing data and plots.
回答3:
You can set spacing with margins()
import datetime
import matplotlib.pyplot as plt
dates = [datetime.date(2002, 3, 11) - datetime.timedelta(days=x) for x in range(0, 10)]
yvalues = [2, 4, 1,7,9,2, 4, 1,7,9]
errorvalues = [0.4, 0.1, 0.3,0.4, 0.1,.4, 0.1, 0.3,0.4, 0.1]
fig = plt.figure()
ax = fig.add_subplot(1, 1, 1)
ax.errorbar(dates,yvalues,yerr=errorvalues,fmt='.')
ax.margins(x=0.05)
fig.autofmt_xdate()
plt.show()
来源：https://stackoverflow.com/questions/30445708/datetime-axis-spacing