Split matrices by row

split_matrix.R

#' Split a matrix by row much as is done for \code{data.frame}
#'
#' @param x the matrix
#' @param f a ‘factor’ see \code{split}
#' @param ... other arguments passed to \code{split}
#' @return a list of matrices
split_matrix <- function(x, f, ...){

    rnm <- rownames(x)
    if (is.null(rnm)){
        rnm <- seq_len(nrow(x))
    }
    ix <- split(rnm, f, ...)
    lapply(ix,
        function(i, data = NULL){
            data[i,]
        }, data = x)
}