Matplotlib's hist says "Compute and draw the histogram of x". I'd like to make a plot without computing anything first. I have the bin widths (unequal), and the total amount in each bin, and I want to plot a frequency-quantity histogram.
For instance, with the data
cm Frequency
65-75 2
75-80 7
80-90 21
90-105 15
105-110 12
It should make a plot like this:
http://www.gcsemathstutor.com/histograms.php
where the area of the blocks represents the frequency in each class.
You want a bar chart:
import numpy as np
import matplotlib.pyplot as plt
x = np.sort(np.random.rand(6))
y = np.random.rand(5)
plt.bar(x[:-1], y, width=x[1:] - x[:-1], align='edge')
plt.show()
Here x contains the edges of the bars and y contains the height (not the area!). Note that there is one more element in x than in y because there is one more edge than there are bars.
With original data and area calculation:
from __future__ import division
import numpy as np
import matplotlib.pyplot as plt
frequencies = np.array([2, 7, 21, 15, 12])
bins = np.array([65, 75, 80, 90, 105, 110])
widths = bins[1:] - bins[:-1]
heights = frequencies/widths
plt.bar(bins[:-1], heights, width=widths, align='edge')
plt.show()
Working on the same as David Zwicker:
import numpy as np
import matplotlib.pyplot as plt
freqs = np.array([2, 7, 21, 15, 12])
bins = np.array([65, 75, 80, 90, 105, 110])
widths = bins[1:] - bins[:-1]
heights = freqs.astype(np.float)/widths
plt.fill_between(bins.repeat(2)[1:-1], heights.repeat(2), facecolor='steelblue')
plt.show()
