R/colSds.R

In AEBilgrau/Bmisc: Biostatistical miscellaneous functions

#' @name colSds
#' @aliases rowSds colSds
#' @title Compute row and column standard deviations
#' @description The \code{rowSds} and \code{colSds} respectively computes the 
#'   standard deviations of the rows and columns of the given matrix.
#' @param x A numeric matrix of size \code{n} times \code{m}
#' @return \code{colSds} returns a numeric vector of length \code{m}.
#' @author Anders Ellern Bilgrau <anders.ellern.bilgrau (at) gmail.com>
#' @seealso \code{\link{rowMeans}}, \code{\link{colMeans}}
#' @examples
#' x <- matrix(rnorm(50), 10, 5)
#' colSds(x)
#' @export
colSds <- function(x) {
  n <- nrow(x)
  means <- colMeans(x)
  return(sqrt(colMeans((x - means)^2)*(n/(n - 1))))
}