poputils (version 0.4.1)

to_matrix: Build a Matrix from Measure and ID Variables

Description

Build a matrix where the elements are values of a measure variable, and the rows and columns are formed by observed combinations of ID variables. The ID variables picked out by rows and cols must uniquely identify cells. to_matrix(), unlike stats::xtabs(), does not sum across multiple combinations of ID variables.

Usage

to_matrix(x, rows, cols, measure)

Value

A matrix

Arguments

x

A data frame.

rows

The ID variable(s) used to distinguish rows in the matrix.

cols

The ID variable(s) used to distinguish columns in the matrix.

measure

The measure variable, eg rates or counts.

Examples

x <- expand.grid(age = c(0, 1, 2),
                 sex = c("F", "M"),
                 region = c("A", "B"),
                 year = 2000:2001)
x$count <- 1:24

to_matrix(x,
          rows = c(age, sex),
          cols = c(region, year),
          measure = count)

to_matrix(x,
          rows = c(age, sex, region),
          cols = year,
          measure = count)

## cells not uniquely identified
try(
to_matrix(x,
          rows = age,
          cols = sex,
          measure = count)
)