Machine Learning with Spark - Second Edition

Categorical features

Categorical features cannot be used as input in their raw form, as they are not numbers; instead, they are members of a set of possible values that the variable can take. In the example mentioned earlier, user occupation is a categorical variable that can take the value of student, programmer, and so on.

To transform categorical variables into a numerical representation, we can use a common approach known as 1-of-k encoding. An approach such as 1-of-k encoding is required to represent.

An approach such as 1-of-k encoding is required to represent nominal variables in a way that makes sense for machine learning tasks. Ordinal variables might be used in their raw form but are often encoded in the same way as nominal variables. ...