The use of selected sub-areas of the matrix may be very usefully applied in this context. Suppose you wish to add 50% of the trips for origin 6 from the second input .ufm file to the internal matrix. To do so first use the select procedures to select row 6 (all columns), then use the equation:
The selection of single rows and/or columns may also be very usefully applied to setting the row/column values for newly created zones; see 10.4.2.