40 Algorithms Every Programmer Should Know

Row selection

Each row in a DataFrame corresponds to a data point in our problem space. We need to perform row selection if we want to create a subset of the data elements we have in our problem space. This subset can be created by using one of the two following methods:

• By specifying their position

• By specifying a filter

A subset of rows can be retrieved by its position as follows:

>>> df.iloc[1:3,:]  id name age decision1 2 Elena 23 False2 3 Steven 40 True

Note that the preceding code will return the first two rows and all columns.

To create a subset by specifying the filter, we need to use one or more columns to define the selection criterion. For example, a subset of data elements can be selected by this method, as follows:

>>> df[df.age>30] ...