R/method2_paleyII.R

In HadamardR: Hadamard Matrix Generation

#' method2_paleyII
#'
#' method2_paleyII is internal function not exported.
#'
#' @param n  integer (order of the matrix)
#' @return 0 or (n/4)-1
#' @details
#' this function checks q<- (n/4)-1, q is prime number and q = 1(mod 4). if it satisfy it returns q;
#' otherwise returns NULL.
#'
#' @references
#' Paley, R.E.A.C. (1933). On Orthogonal matrices. J. Combin. Theory, A 57(1), 86-108.



method2_paleyII<-function(n){
  q<- (n/4)-1
  if(is.prime(q)==T & numbers::mod(q,4)==1)
    return(q)
  else{
    return(0)
  }
}