Filtering

Until now, you have learned how to do several kinds of calculations which enriched the set of data. There is still another kind of operation that is frequently used, and does not have anything to do with enriching the data, but with discarding the data. It is called filtering unwanted data. Now, you will learn how to discard rows under given conditions. As there are several kinds of filters that we may want to apply, let's split this section into two parts: Counting frequent words by filtering and Refining the counting task by filtering even more.