title: Could not convert string to float: 'Neudorf'
body: <p>I have a dataframe df which contains a float column num. It looks like
  None
  0.00
  ...
  0.00
  0.00
  0.00</p>
  <p>In data frame num is in object data type. So I'm trying to convert it to float data type in databricks Runtime 7. I'm using following command</p>
  <pre><code>df['num']=df['num'].astype(float)
  </code></pre>
  <p>But I'm getting error message</p>
  <pre><code>could not convert string to float: 'Neudorf'
  </code></pre>
  <p>Can you help me to resolve the issue?</p>