R/fold_180.R

In Swarchal/phenoDist: Distance Measurements in Phenotypic Screening

#' Constrains numbers to 180
#'
#' Limits a numerical vector to 180. If an element in the vector is greater
#'  than 180 then the amount it is greater than 180 by is subtracted from it.
#'  Useful for angles between two vectors, if the angle between two vectors
#'  is 180 degrees this is the maximum difference -- once the angle exceeds
#'  180 degrees the vectors begin to converge again.
#' 
#' @param x Vector of angles (in degrees)
#' @return Numerical vector
#'
#' @export
#'
#' @examples
#' sample <- seq(1, 360, 1)
#' fold_180(sample)


fold_180 <- function(x){

  if (!is.vector(x)) stop("Expecting a vector")
  if (!is.numeric(x)) stop("Expecting numerical values")
  if (max(x) > 360){
  	warning("Input values exceed 360, will produce negative values")
  }

  out <- ifelse(x > 180,  360 - x, x)
  out
}