In Chapter 10, Selecting Subsets of Data, we marked every row as True
or False
before filtering out the False
rows. In a similar fashion, it is possible to mark entire groups of data as either True
or False
before filtering out the False
groups. To do this, we first form groups with the groupby
method and then apply the filter
method. The filter
method accepts a function that must return either True
or False
to indicate whether a group is kept or not.
Note
This filter
method applied after a call to the groupby
method is completely different than the DataFrame filter
method.
In this recipe, we use the college dataset to find all the states that have more non-white undergraduate students than white. As this is a dataset from the US, whites form the majority and therefore, we are looking for states with a minority majority.