title: Create new dataframe by substracting every column with each other, solving poor performance issues
body: <p>Error:</p>
  <blockquote>
  <p>&quot;DataFrame is highly fragmented.  This is usually the result of
  calling <code>frame.insert</code> many times, which has poor performance.
  Consider joining all columns at once using pd.concat(axis=1) instead.
  To get a de-fragmented frame, use `newframe = frame.copy()&quot;</p>
  </blockquote>
  <p>Code:</p>
  <pre><code>df_DIFFs = pd.DataFrame()
  
  for a, b in itertools.permutations(df.columns,2):
      df_DIFFs[f'{a}-{b}'] = df[a] - df[b]
  
  df_DIFFs
  </code></pre>
  <p>I can't imagine how to use pd.concat or any other more efficient solution in this situation.
  Thanks.</p>