R/GetRowCol.R

In ICvectorfields: Vector Fields from Spatial Time Series of Population Abundance

#' Retrieve matrix row and column indices
#'
#' Here is a function that will find the row and column indices of a matrix that
#' are associated with a vector index.
#'
#' Often when applying functions like the R function which.max(matrix) to a
#' matrix, a vector index is returned when the coder would prefer to have a row
#' and column indices. This function converts the vector index to row and column
#' indices.
#'
#' The function assumes that the elements of the matrix are filled by column
#' (byrow = FALSE), which is the default R matrix behaviour.
#'
#' @param Index an integer vector index
#' @param dim1 integer row dimension of the matrix from which the row and column
#'   indices are to be extracted
#' @param dim2 integer column dimension of the matrix from which the row and
#'   column indices are to be extracted
#'
#' @return a numeric vector of length two with two integers indicating row and
#'   column respectively
#' @export
#'
#' @examples
#' GetRowCol(6, dim1 = 3, dim2 = 3) # should return c(3, 2)
GetRowCol <- function(Index, dim1, dim2) {
  Col1 <- ceiling(Index / dim1)
  Row1 <- Index - (Col1 - 1) * dim1
  return(c(Row1, Col1))
}