In this section, we cover data transformation which is the creation of new columns in a table or the modification of
existing columns typically as a function of one or more existing columns.
This section is organized as follows:
Basic Transformation where we cover the basic yet commonly
used data transformation scenarios. For instance, create a new column that is the ratio of two existing columns.
Conditional Transformation where we cover how to carry
out data transformation operations conditionally. In other words, we wish to modify the values of the column for some
rows differently from others based on one or more conditions. For instance, we wish to cap the values of a column to a
certain range by setting values outside the range to the limits of the range while not changing values that fall
within the range.
Grouped Transformation where we cover how to carry out
data transformation within groups. For instance, we wish to subtract from a column the mean value for each group,
where the group is defined by another column.