R/times.R

In matlab2r: Translation Layer from MATLAB to R

#' @title Element-wise matrix multiplication
#' @description Emulates the `times()` and `.*` operators from Matlab.
#' @details This function basically handles elements of different length
#' better than the `*` operator in R, at least as far as behavior from a
#' Matlab user is expecting.
#' @param a first factor of the multiplication
#' @param b second factor of the multiplication
#' @returns matrix with dimensions equal to the larger of the two factors
#' @export
#' @examples
#' times(9, 6)
#' x <- matrix(1:4, 2)
#' y <- c(10, 3)
#' print(x)
#' print(y)
#' times(x, y)
#' x * y
times <- function(a, b) {
  # Converting everything to matrix because Matlab looooooves the matrix
  a <- as.matrix(a)
  b <- as.matrix(b)

  dominant_mx <- NULL
  if (!all(dim(a) == dim(b))) {
    if (all(dim(a) >= dim(b))) {
      dominant_mx <- a
      dominated_mx <- b
    } else if (all(dim(b) >= dim(a))) {
      dominant_mx <- b
      dominated_mx <- a
    } else {
      dominant_mx <- "neither"
      dominant_dim <- c(
        base::max(nrow(b), nrow(a)), base::max(ncol(b), ncol(a))
      )
    }
  }

  if (is.null(dominant_mx)) {
    out <- a * b
  } else if (dominant_mx[1] == "neither") {
    a <- repmat(
      mx = a,
      n = c(dominant_dim[1] - nrow(a) + 1, dominant_dim[2] - ncol(a) + 1)
    )
    b <- repmat(
      mx = b,
      n = c(dominant_dim[1] - nrow(b) + 1, dominant_dim[2] - ncol(b) + 1)
    )
    out <- a * b
  } else {
    # Expanding dominated matrix
    dominated_mx <- repmat(
      mx = dominated_mx,
      n = c(
        nrow(dominant_mx) - nrow(dominated_mx) + 1,
        ncol(dominant_mx) - ncol(dominated_mx) + 1
      )
    )
    out <- dominant_mx * dominated_mx
  }
  return(out)
}