R/fo_areatri.R

In spacea/projekt.2019.pacocha: Figure operations

#' Triangle area
#'
#' @description Function which calculates an area of a triangle.
#'
#' @param x1 Value of the first point on the X axis.
#' @param x2 Value of the second point on the X axis.
#' @param x3 Value of the third point on the X axis.
#' @param y1 Value of the first point on the Y axis.
#' @param y2 Value of the second point on the Y axis.
#' @param y3 Value of the third point on the Y axis.
#'
#' @return Numeric value
#' @export
#'
#' @examples
#' fo_area_tri(2,0,10,10,5,3)
fo_area_tri <- function(x1, y1, x2, y2, x3, y3){
  if(is.numeric(x1) == FALSE){
    stop("First argument is non-numeric")
  } else if(is.numeric(y1) == FALSE){
    stop("Second argument is non-numeric")
  } else if(is.numeric(x2) == FALSE){
    stop("Third argument is non-numeric")
  } else if(is.numeric(y2) == FALSE){
    stop("Fourth argument is non-numeric")
  } else if(is.numeric(x3) == FALSE){
    stop("Fifth argument is non-numeric")
  } else if(is.numeric(y3) == FALSE){
    stop("Sixth argument is non-numeric")
  } else {
    (1/2) * abs((x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1))
  }
}