Roles Come First - Train-Only Preprocessing, Exactly

Start by marking which rows are train and which row is test.

highlighted = computed this step

Show the role column

Rows A and B are train rows. Row C is a test row.

A,B:\text{ train}\quad C:\text{ test}

The x values are 0, 10, and 20.

x_A=0,\quad x_B=10,\quad x_C=20

Row C is visible as the test row. It is not used to fit the train-only min and max.

\text{fit uses train rows only}