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I want to plot a bar graph with a variable amount of values along the x-axis. For the data, I have a set of labels which I want to show on the x-axis under the bars. I also want the x-axis limits to start at -1, since otherwise, only half of the first bar at index 0 would be visible. I've tried multiple alternatives for achieving that, none of them worked, because the xticklabels are always one or more off. And IF they work for a given set of data, with another set of data (with more or less bars) it does not work again. See minimum code example below

from matplotlib import pyplot as plt
from matplotlib import ticker
import numpy as np

randData = np.random.rand(100)
xValues = np.linspace(0, len(randData)-1, num=len(randData))

labels = []
for i in range(len(randData)):
    labels.append('label' + str(i))

fig, ax = plt.subplots()
ax.bar(np.linspace(0, len(randData)-1, num=len(randData)), randData)
ax.xaxis.set_major_locator(ticker.MultipleLocator(1))

# Alternative 1
# Use an empty string for index -1, set labels, then set new xlim
labels.insert(0, '')
ax.set_xticklabels(labels, size='x-small', rotation=90)
plt.xlim(-1, len(randData))

# Alternative 2
# Use an empty string for index -1, set new xlim, then set labels
labels.insert(0, '')
plt.xlim(-1, len(randData))
ax.set_xticklabels(labels, size='x-small', rotation=90)

# Alternative 3
# Setting limits with ax.set_xlim
ax.set_xticklabels(labels, size='x-small', rotation=90)
ax.set_xlim([-1, len(randData)])

# Alternative 4
# Setting limits with plt.xlim
ax.set_xticklabels(labels, size='x-small', rotation=90)
plt.xlim(-1, len(randData))

plt.show()

None of the variants worked so far. One part of the problem is that the pyplot automatically sets its xlimits depending on the amount of bar graphs (sometimes it starts at -1, with more values it might sometimes start at -4).

One of the faulty results is shown below: Bar graph with wrong xticklabels

Any help would be appreciated.

P.S.: If I may, I'd like to add a little side question: How can I remove the Warning "UserWarning: FixedFormatter should only be used together with FixedLocator" when setting the xticklabels? Nothing from this answer worked for me.

Trenton McKinney
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drdolphin
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    You really shouldn't use `ax.xaxis.set_major_locator(ticker.MultipleLocator(1))` here. That may add too many tick positions. Just use `xvalues = np.arange(len(randData))`, `ax.bar(xvalues, randData)`, `ax.set_xticks(xvalues)` and `ax.set_xticklabels(labels, ...)`. You better don't change the xlimits manually, but instead just use the defaults and maybe use `ax.margins(x=0.02)` if you want them smaller. – JohanC Dec 09 '21 at 18:08

0 Answers0