It is also possible to use input from an ascii file to “update” all or part of the current internal matrix (presumably read from an existing .ufm matrix) rather than writing it “from scratch”. The choice between “build” and “update” is made immediately on entering the top menu under Build/Update.
Matrix update data may use only some of the standard data input format conventions described below; i.e., user-defined records (10.5.3), individual cell records (10.5.4) and spreadsheets (10.5.5). Thus the standard SATURN format is not available as an update option since, by construction, it must contain all cell values.
The data set read need not contain all ij cell values but may be only a subset which, in the case of user-defined and spreadsheet formats, must constitute a “rectangle” within the matrix as defined by upper and lower row and column numbers.
An update may either “replace” the existing cell value by the value which is read in or “increment” it (i.e., add the existing and the input cell values together).
An advantage of updating an existing .ufm matrix rather than creating one totally from scratch is that with updates the number of rows and columns plus any “names” (see below) are pre-defined, only (certain) cell values are set.