R/redu.modp.R

In crossdes: Construction of Crossover Designs

redu.modp <- function(a, b, p) {
  
  la <- length(a)
  lb <- length(b)
  b1 <- b/b[1]  # divide by coefficient of highest power
  
  dummy <- numeric(la)  # partial result to be subtracted
  
  for (i in 1:(la - lb + 1)) {
    dummy <- rep(0, la)
    dummy[i:(i + lb - 1)] <- a[i] * b1
    a <- (a - dummy)%%p
  }
  a[(la - lb + 2):la]
}