The initial application is in the management of cohort data consisting of many subsets defined by the tree structure. The data record progression over time through a sequence of ordered states. Subroutine used by plpc, cumulative sums of columns. The object has only one node, the root. It is assumed the analyst will construct the model.
Columns represent successive time points.
The column sums are constant and equal to the number of students in the data. The row values show the number of students in each class at each time period. By default, the data is assumed to be observed on a semester basis. Force common horizontal scaling for multiple cohorts, some of which may have censored data. The user must open a plotting device before using this function.