R/chi.square.2d.expected.frequencies.R

In burrm/lolcat: Miscellaneous Useful Functions

#' Expected Cell Frequencies  
#' 
#' Calculates expected cell frequencies for a given matrix.
#'
#' @param observed.frequencies A matrix of values to use to calculate expected cell frequencies.
#'
#' @return A matrix with expected cell frequencies matching the dimensions of observed.frequencies.
chi.square.2d.expected.frequencies <- function(
  observed.frequencies
) {
  ret <- observed.frequencies

  nc <- ncol(observed.frequencies)
  nr <- nrow(observed.frequencies)
    
  observed.frequencies <- xt.sums(observed.frequencies)
  
  for (i in 1:nr) {
    for (j in 1:nc) {
      ret[i,j] <-  observed.frequencies[i,(nc+1)]*observed.frequencies[(nr+1),j]/observed.frequencies[(nr+1),(nc+1)]
    }
  }
  
  ret
}