def summary_stats(x, y, nm=None):
<EOL>if isinstance(nm, str):<EOL><INDENT>nm = [nm]<EOL>
Compute summary statistics for paired x, y data.

Tests
-----

Parameters
----------
x, y : array-like
    Data to compare
nm : str (optional)
    Index value of created dataframe.

Returns
-------
pandas dataframe of statistics.