Pandas: convert categories to numbers
<p>Suppose I have a dataframe with countries that goes as:</p>

<pre><code>cc | temp
US | 37.0
CA | 12.0
US | 35.0
AU | 20.0
</code></pre>

<p>I know that there is a pd.get_dummies function to convert the countries to 'one-hot encodings'. However, I wish to convert them to indices instead such that I will get <code>cc_index = [1,2,1,3]</code> instead. </p>

<p>I'm assuming that there is a faster way than using the get_dummies along with a numpy where clause as shown below:</p>

<p><code>[np.where(x) for x in df.cc.get_dummies().values]</code></p>

<p>This is somewhat easier to do in R using 'factors' so I'm hoping pandas has something similar.</p>