R/findPowers.R

In wesleyburr/tsinterp: Time Series Interpolation

#' Find Powers
#'
#' @param N 
#' @param f0 
#' @param Nyq 
#' @param prec 
#'
#' @return
#' @export
#'
#' @examples
 

findPowers <- function(N,f0,Nyq,prec) {
  if(N < 0){
    stop("N must be greater than or equal to 0")
  }
  
  nFFT <- 1e30
  
  low2 <- 0
  high2 <- floor(log(N,2))+2
  low3 <- 0
  high3 <- floor(log(N,3))+2
  low5 <- 0
  high5 <- floor(log(N,5))+2
  low7 <- 0
  high7 <- floor(log(N,7))+2
  for(i in low2:high2) {
    for(j in low3:high3) {
      for(k in low5:high5) {
        for(l in low7:high7) {
          att <- 2^i * 3^j * 5^k * 7^l
          if((att > 2*N) & att < 100*N) {
            df <- (Nyq*2)/att
            if( abs(trunc(f0/df)*df - f0) < prec ) {
              if(att < nFFT) {
                nFFT <- att 
              }
            }
          } # big enough
        } # end of 7
      } # end of 5
    } # end of 3
  } # end of 2
  if(nFFT == 1e30) {
    return(-1)
  } else {
    return(nFFT)
  }
}