progression_matrix: Build the projection matrix

In enrollcast: Project School Enrollment with Grade Progression Ratios

Build the projection matrix

Description

Assembles the projection matrix used to advance enrollment. Progression ratios are placed on the sub-diagonal (each non-entry grade is fed by the grade below); the entry-grade row is left at zero because entry enrollment is supplied exogenously to project_enrollment(). The ratios must form a single low-to-high chain: each grade_to must be the grade immediately above its grade_from in the resolved order.

Usage

progression_matrix(ratios, grade_order = NULL)

Arguments

ratios	A data frame or data-frame subclass with columns grade_from, grade_to, and ratio, as returned by progression_ratios(). grade_from and grade_to must not be missing. ratio must be numeric, non-negative, and finite; an infinite ratio (from a zero-enrollment feeder) is rejected, while NA/NaN ratios (e.g. from sparse history) are kept in the matrix with a warning.
grade_order	Optional character vector giving the low-to-high grade order. If omitted, the order is reconstructed from the transition chain. Every non-entry grade in grade_order must appear as a grade_to in ratios. Must not contain duplicates or missing values.

Value

A square numeric matrix with grade dimnames.

Examples

ratios <- data.frame(
  grade_from = c("K", "1"),
  grade_to = c("1", "2"),
  ratio = c(0.92, 0.97)
)
progression_matrix(ratios)

enrollcast documentation built on Aug. 27, 2026, 1:08 a.m.