Question Q7.4.2
Adapt Example E7.7 to produce a horizontal bar chart, with the bars in order of decreasing letter frequency (i.e. with the most common letter, E, at the bottom).
Solution Q7.4.2
This solution uses orientation='horizontal' to produce a horizontal bar chart and reverses the $y$-axis to put the highest-frequency letter at the bottom.
import numpy as np
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.pyplot as plt
text_file = 'moby-dick.txt'
letters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
# Initialize the dictionary of letter counts: {'A': 0, 'B': 0, ...}
lcount = dict([(l, 0) for l in letters])
# Read in the text and count the letter occurences
for l in open(text_file).read():
try:
lcount[l.upper()] += 1
except KeyError:
pass
# The total number of letters for normalization
norm = sum(lcount.values())
# A sorted list of (freq, letter) pairs
lfreqs = sorted([(v / norm * 100,k) for k, v in lcount.items()])
fig = plt.figure()
ax = fig.add_subplot(111)
# The bar chart, with letters along the horizontal axis and the calculated
# letter frequencies as percentages as the bar height
y = range(26)
ax.bar(left=0, bottom=y, width=[item[0] for item in lfreqs],
height=0.8, color='g', alpha=0.5, align='center',
orientation='horizontal')
ax.set_yticks(y)
ax.set_yticklabels([item[1] for item in lfreqs])
ax.tick_params(axis='y', direction='out')
# NB We want the most common letter at the bottom of our chart, so reverse y:
ax.set_ylim(25.5, -0.5)
ax.xaxis.grid(True)
ax.set_xlabel('Letter frequency, %')
plt.show()
