Marks the column(s) we would like to predict.
columnscontain the variables we want to predict. They are not used by the feature learning algorithm unless we explicitly tell it to do so (refer to
join()). But they are such an important part of the analysis that the population table is required to contain at least one of them (refer to Tables).
The content of the target columns needs to be numerical. For classification problems, target variables can only assume the values 0 or 1. Target variables can never be NULL.