Find max value and the corresponding column/index name in entire dataframe
<p>I want to select the maximum value in a dataframe, and then find out the index and the column name of that value.
Is there a way to do it?</p>

<p>Say, in the example below, I want to first find the max value (<code>31</code>), and then return the index and column name of that value <code>(20, R20D)</code></p>

<pre><code>a = pd.DataFrame({'R05D':[1,2,3],'R10D':[7,4,3],'R20D':[31,2,4]},index=[20,25,30])
</code></pre>

<p>Thanks!</p>