R/p2fc.R

In jrevenaugh/TSAUMN: Time Series Analysis Tools Used in ESCI5201 at the University of Minnesota

#' Convert corner periods to fc specification for cosfilt
#'
#' cosfilt assumes a frequency range of 0 (DC) to 0.5 (Nyquist).  p2fc converts native
#' unit periods to cosfilt corner frequencies.
#' @param deltat sampling interval
#' @param pc vector of corner periods
#' @export
#' @examples
#' t <- seq( 0, 500, 2 )
#' x <- rnorm( length( t ) ) + 100 * sin( 2 * pi * t / 20 )
#' x.ts <- ts( x, deltat = 2 )
#' pc <- c( 4, 10, 30, 40 )
#' fc <- p2fc( 2, pc )
#' f.ts <- cosfilt( x.ts, fc, fw = c( 0, 1, 1, 0 ) )
#' plot( x.ts )
#' lines( f.ts, col = "red" )

p2fc <- function( deltat = 1, pc ) {
  fc <- sort( 1 / pc )
  return( fc * deltat )
}