title: pandas groupby dropping columns
body: <p>I'm doing a simple group by operation, trying to compare group means. As you can see below, I have selected specific columns from a larger dataframe, from which all missing values have been removed.</p>
  
  <p><img src="https://i.stack.imgur.com/y8EEI.png" alt="selected columns and df head"></p>
  
  <p>But when I group by, I am losing a couple of columns:</p>
  
  <p><img src="https://i.stack.imgur.com/AxO9H.png" alt="group-by logic and resulting df"></p>
  
  <p>I have never encountered this with pandas, and I'm not finding anything else on stack overflow that is all that similar. Does anybody have any insight?</p>