title: Memory pointers: modifying dataframes in python pandas
body: <p>supposed I have an <code>n x n</code> dataframe <code>d1</code> in pandas. I then take a subset of <code>d1</code> and create another dataframe that is <code>m x m</code> where <code>m &lt; n</code>, call it <code>d2</code>. When I modify <code>d2</code>, I want those same changes to appear in the "parent" dataframe, <code>d1</code>. Thus I want <code>d2</code> to just be a memory pointer to that subset of <code>d1</code>. How would I do this?</p>