title: Could not convert string to float: 'Mazda RX4' using SimpleImputer
body: <p>I was trying to load mtcars.csv file into a dataframe and trying to replace the missing data with variable name. In my data set, i have missing value at <code>df[2,4]</code>, 3rd row and 5th column (Column name <code>hp</code>).</p>
  <p><a href="https://i.stack.imgur.com/h6B1P.png" rel="nofollow noreferrer">Dataset</a></p>
  <p>I am using the following code for mean imputation:</p>
  <pre><code>from sklearn.impute import SimpleImputer 
  imputer=SimpleImputer(missing_values=n.nan,strategy='mean')
  imputer=imputer.fit(df)
  df=imputer.transform(df)
  </code></pre>
  <p>But getting value error as below:</p>
  <p><a href="https://i.stack.imgur.com/vM3U4.png" rel="nofollow noreferrer">error screenshot</a></p>
  <p>Can anyone please help me to get a solution for replacing the missing value in my data set with mean.</p>