Bug report

Bug summary

Categorical (i.e. string) xdata inputs get sorted before plotting.

Code for reproduction

plt.bar(["b","a","c"], [2,1,3])

Actual outcome

Bars appear in the order "a", "b", "c".

Expected outcome

Bars appear in the order of the input, so "b", "a", "c".

Matplotlib version

• Operating system: Arch Linux
• Matplotlib version: 2.1
• Matplotlib backend (print(matplotlib.get_backend())): qt5agg
• Python version: 3.6
• Jupyter version (if applicable):
• Other libraries: