extract <- function(dat, klev)
{
#     Function to extract coefficients of level klev given an object of class
#     wd
  n <- length(dat$D) + 1
  maxlev <- log(n, base = 2) - 1
  if(klev > maxlev || klev < 0) {
    cat("Not a valid level number.\n")
    0
  }
  else {
    istart <- n - (2^(klev + 1) - 1)
    dat$D[istart:(istart + 2^klev - 1)]
  }
}