Partial Identity

To fill a section of the design matrix with an identity matrix, select the FillCol | Partial Identity choices. You are asked for the number of rows (and hence columns) to fill with an identity matrix. This command is useful for filling the matrix with a discrete effect for multiple parameters. As an example, suppose the following design matrix is on the screen, consisting of all zeros, with the cursor at the highlighted (underlined) cell.

In response to the request for the number of rows and columns to fill, you say 5. After this entry, this subsection of the design matrix is filled with an identity matrix. The matrix would look like this.