R/matrixOps.R

In rvec: Vectors Representing Random Variables

## Matrix multiplication

## requires R(>= 4.30), since matrixOps introduced in v4.3

#' Matrix Multiplication with Rvecs
#'
#' Matrix multiplication `%*%` can be used
#' with [rvecs][rvec()]. However, in constrast to
#' standard R vectors, multiplying an rvec
#' by a matrix does not produce a row or
#' column vector. Instead it produces an
#' ordinary rvec, with no dimensions.
#'
#' @param x,y Vectors, matrices, or rvecs.
#'
#' @returns An rvec, if `x` or `y`
#' is an rvec.
#'
#' @examples
#' A <- matrix(c(10, 10, 10,
#'               11, 11, 11),
#'             nrow = 2, byrow = TRUE)
#' x <- rvec(list(c(1, 2),
#'                c(3, 4),
#'                c(5, 6)))
#' A %*% x
#'
#' ## matrix multiplication with an
#' ## ordinary R matrix produces
#' ## a row or column vector
#' y <- c(1, 3, 5)
#' A %*% y
#' @method matrixOps rvec
#' @export
matrixOps.rvec <- function(x, y) {
    is_rvec_x <- is_rvec(x)
    is_rvec_y <- is_rvec(y)
    if (is_rvec_x && is_rvec_y) 
        ans <- sum(x * y)
    else if (!is_rvec_x && is_rvec_y) {
        my <- field(y, "data")
        ans <- x %*% my
        ans <- rvec(ans)
    }
    else {
        mx <- field(x, "data")
        ans <- t(crossprod(mx, y))
        ans <- rvec(ans)
    }
    ans
}



## Something weird happening with argument names. Version below
## works with ubunto-dev but not other tests.
## #' Matrix multiplication with rvecs
## #'
## #' Matrix multiplication `%*%` can be used
## #' with [rvecs][rvec()]. However, in constrast to
## #' standard R vectors, multiplying an rvec
## #' by a matrix does not produce a row or
## #' column vector. Instead it produces an
## #' ordinary rvec, with no dimensions.
## #'
## #' @param x,y Vectors, matrices, or rvecs.
## #'
## #' @returns An rvec, if `x` or `y`
## #' is an rvec.
## #'
## #' @examples
## #' A <- matrix(c(10, 10, 10,
## #'               11, 11, 11),
## #'             nrow = 2, byrow = TRUE)
## #' x <- rvec(list(c(1, 2),
## #'                c(3, 4),
## #'                c(5, 6)))
## #' A %*% x
## #'
## #' ## matrix multiplication with an
## #' ## ordinary R matrix produces
## #' ## a row or column vector
## #' y <- c(1, 3, 5)
## #' A %*% y
## #' @method matrixOps rvec
## #' @export
## matrixOps.rvec <- function(x, y) {
##     is_rvec_x <- is_rvec(x)
##     is_rvec_y <- is_rvec(y)
##     if (is_rvec_x && is_rvec_y) 
##         ans <- sum(x * y)
##     else if (!is_rvec_x && is_rvec_y) {
##         my <- field(y, "data")
##         ans <- x %*% my
##         ans <- rvec(ans)
##     }
##     else {
##         mx <- field(x, "data")
##         ans <- t(crossprod(mx, y))
##         ans <- rvec(ans)
##     }
##     ans
## }