title: how to corectly plot grouped pandas series with string and numbers in different columns
body: <p>data looks like this:</p>
  <p><a href="https://i.stack.imgur.com/eRZjR.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eRZjR.jpg" alt="enter image description here" /></a></p>
  <pre><code> col1  col2
   1     med
   1     low
   1     high
   2     high
   3     low
   2     high
   3     low
  </code></pre>
  <p>there is two columns, i want to group col2 and count each item in col1, e.g. how many ones
  and twos have 'maRali' feature.</p>
  <p>used get_dummies to convert categorical variables to numeric, but while plotting get error:</p>
  <pre><code>TypeError: 'DataFrame' objects are mutable, thus they cannot be hashed
  </code></pre>
  <p>here is the whole code:</p>
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  
  import pandas as pd
  
  data = data = pd.read_csv(r&quot;C:\Users\givi.jalaghania\.spyder-py3\07_maragebi.csv&quot;)
  
  to_numeric = pd.get_dummies(data['riskiaobis done'])
  
  
  ct = ['datvla']
  
  
  # data.groupby(ct).agg('count').plot(kind = 'bar')
  
  
  data.groupby(ct, to_numeric).size()
  </code></pre>