R/rhombi.R

In inSileco/graphicsutils: Collection of graphics utilities

#' Rhombi
#'
#' Add rhombi on a plot and returns areas.
#'
#' @param x a vector of x coordinates of the centers of the losange
#' @param y a vector of y coordinates of the centers of the losange
#' @param ldg vector of length of the large diagonals.
#' @param sdg vector of length of the small diagonals.
#' @param rot rotation angles (in degree) of the rhombi.
#' @param add logical. If `TRUE` rhombi are added to the current plot (default
#' behavior).
#' @param ... additional arguments to be passed to [graphics::polygon()]
#' function.
#'
#' @keywords rhumbus
#'
#' @export
#'
#' @details
#' The number of rhombus maximal is provided by the length of the largest
#' argument among x, y, ldg, sdg and rot. Other arguments are repeated with the
#' largest length as the desired one (see [rep_len()]).
#' Additional arguments remain the same for every rhombus.
#'
#' @return
#' A vector including rhombi areas is returned if assigned.
#'
#' @examples
#' # Example 1:
#' plot0(asp = 1)
#' rhombi(0)
#'
#' # Example 2:
#' plot0(c(-0.4, 1.4), c(-0.4, 1.4))
#' rhombi(runif(6), runif(5), runif(2), runif(3))
#'
#' # Example 3:
#' plot0(asp = 1)
#' rhombi(x = 0, rot = seq(0, 180, 20), col = 2, border = NA)
#' rhombi(x = 0, rot = seq(0, 180, 30), ldg = 0.5, col = 7, border = NA)
#'
rhombi <- function(x, y = x, ldg = 1, sdg = ldg, rot = 0, add = FALSE, ...) {
    sz <- max(lengths(list(x, y, ldg, sdg, rot)))
    x <- rep_len(x, sz)
    y <- rep_len(y, sz)
    ldg <- rep_len(ldg, sz)
    sdg <- rep_len(sdg, sz)
    rot <- rep_len(rot, sz)
    rot <- pi * rot / 180
    ## ----
    if (add) {
        for (i in seq_len(sz)) {
            corh <- matrix(0, 2, 4)
            corh[1L, ] <- c(.5 * ldg[i], 0, -.5 * ldg[i], 0)
            corh[2L, ] <- c(0, .5 * sdg[i], 0, -.5 * sdg[i])
            mat.rot <- matrix(
                c(cos(rot[i]), sin(rot[i]), -sin(rot[i]), cos(rot[i])),
                2
            )
            pt.los <- mat.rot %*% corh
            polygon(x[i] + pt.los[1, ], y[i] + pt.los[2, ], ...)
        }
    }
    invisible(0.5 * ldg * sdg)
}