如何将 plot 两个 arrays 的数据做成柱状图并排在一起

Question

This might be a very simple question, but I can't figure it out for some reason, and I need to get moving with my work.

If I have two arrays:

a = [3 6 4 9]
b = [4 8 2 7]

and I want to plot them in the form of a histogram, with the pillars next to eachother for each index. How would I go about that?

The x-axis would be like 1, 2, 3, 4 - while the y-axis would be from 0 to 10.

Answer 1

I think you are misunderstanding the concept of histogram, since the x-axis in a histogram is the bins while the y-axis the frequency. By plotting your a and b data in a histogram, you would find 4 bars of height 1 in each set.

I understand that what you have is the processed frequency and want to plot it in arbitrary bins. I would suggest that you use directly the raw data and pyplot.histogram , but to directly plot the data you have shown you may use pyplot.bar :

import random
import numpy
from matplotlib import pyplot

a = [3, 6, 4, 9]
b = [4, 8, 2, 7]

x = numpy.array([0,1,2,3])

pyplot.bar(x, a, 0.3)
pyplot.bar(x + 0.3, b, 0.3)
pyplot.show()

Note the x-axis hack to show the bars next to each other. Probably not what you want if you are willing to implement this for more than once.