There are two variants of the method Least squares, a static and a dynamic variant (Fundamentals: Updating demand matrices using the least squares method).
The dynamic variant is only available in conjunction with the PrT assignment procedure Simulation-based dynamic assignment (SBA) and for matrices of demand segments calculated with timetable-based assignments.
1. On the toolbar, click the 
Open 'Procedure sequence' window button.
The Procedure sequence window opens.
2. To the procedure sequence, at the position of your choice, add the Demand matrix correction procedure of the Matrices category (Setting up and starting the procedure sequence).
3. In the row of the added procedure, click the button in the Reference object(s) column.
The Select demand segments window opens.
4. In the Select mode selection list, select the mode of the demand segments whose matrices you would like to correct.
5. In the Demand segments selection list, select the demand segments whose matrices you would like to correct.
|
Tip: To mark multiple demand segments, press the Ctrl key and keep it pressed while clicking the desired entries one by one. |
|
Note: Since demand matrices in Visum are separate objects that can be assigned to several demand segments, the changes to a matrix affect all demand segments that are linked to the matrix after demand segment selection (Connecting demand matrices and demand segments). |
6. Confirm with OK.
The demand segments selected are adopted in the Reference object(s) column.
7. In the line of the newly inserted procedure, click in the Variant/File column and select the Least squares entry from the drop-down list if you want to select the static variant, and Least squares (dynamic) if you want to select the dynamic variant.
8. Make sure the added procedure is highlighted. Then, in the Operations section, click the Edit button.
The window Demand matrix correction (least squares) or Demand matrix correction (least squares, dynamic) opens.
9. Set the desired parameters ('Least squares’ parameters).
10. Confirm with OK.
11. Execute the procedure (Executing procedures in the procedure sequence).
Matrix correction is executed.
|
Note: You can speed up the calculation of the procedure by providing multiple processor cores for the calculation. The calculation of the flow matrix is then performed in parallel on multiple processor cores (Specifying the number of processor cores to be used). |
