grouping items in a list for a barchart in matplot lib and python

I want to make a bargraph or piechart to see how many times each item in a list is represented. Some dummy data...

mylist = [a,a,b,c,c,c,c,d,d]

What I want is a bar chart that'd reflect (a = 2, b = 1, c = 4 etc...)

In reality, I have a much longer list and it is not something to do manually. I started to make a "for loop" that'd compare each item with the previous, and create a new list if different than the last, but even that seems cumbersome. There has to be a simple and elegant way to do this. I am sorry if this has already been addressed, when searching I either get results too simple or overly complicated. This got tagged as a duplicate for how to count elements in a list, this is different because it also addresses the graphing.

3 Answers
3

What you can do is just to iterate over the list and update the dictionary with the frequency of each item.

Example:

import matplotlib.pyplot as plt

mylist = ['a','a','b','c','c','c','c','d','d']

#create a dictionary with the frequency of each item
frequencies =
for item in mylist:
if item in frequencies:
frequencies[item]+=1
else:
frequencies[item] = 1

# plot it
plt.figure()
plt.bar(frequencies.keys(), frequencies.values())
plt.show()


Try using this:

from collections import Counter
mylist = [a,a,b,c,c,c,c,d,d]
Counter(mylist)


Just another solution:

import collections
import matplotlib.pyplot as plt
figure = plt.figure(figsize=(8,6))

mylist = ['a','a','b','c','c','c','c','d','d']
co = collections.Counter(mylist)
plt.bar(range(len(co.keys())), list(co.values()), tick_label=list(co.keys()))
plt.xlabel('Items')
plt.ylabel('Frequency'), list(co.values()), tick_label=list(co.keys()))


Output

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