R/StatByGroup.R

In sethmargolis/PairMeasInv: Applies The Pairwise Method of Examining Measurement Invariance

#' Summarize invariance matrices by group
#' 
#' \code{StatByGroup} applies a descriptive statistic over the rows of each 
#' invariance matrix in a list and returns this as a list of named vectors. 
#' 
#' This function can be used to indicate how invariant each group was with the
#' other groups, in general (e.g., by setting \code{stat.function = median}. 
#' 
#' @param matrix.list A list of invariance matrices from 
#' \code{\link{InvarianceMatrices}}
#' @param stat.function The function to apply over rows
#' @return Thus function returns a list of named vectors. Each vector contains 1
#' element for each group.
#' 
#' @export
StatByGroup <- function(matrix.list, stat.function) {
  # creating list to fill in and output
  out.list <- list()
  # for each invariance matrix, apply the stat.function to each row/column
  for(matrix.number in 1:length(matrix.list)){
    # subset matrix.list to a matrix
    temp.matrix <- matrix.list[[matrix.number]]
    # apply the stat.function over rows
    out.list[[matrix.number]] <-
      sort(apply(temp.matrix, 1, stat.function, na.rm = T))
    # create names for output list
    names(out.list)[matrix.number] <- names(matrix.list)[matrix.number]
  }
  return(out.list)
}