detrend <- function(y,smooth=F,...){

  # Description:
  #
  #   Removes time trend from a time series
  #
  # Usage:
  #
  #   detrend(y,smooth=FALSE,...)
  #
  # Arguments:
  #
  #   y:      a vector containing a time series of data
  #
  #   smooth: Logical. If FALSE (the default) removes linear time trend by 
  #           fitting ordinary least squares regression to the time series y.
  #           If TRUE, then time trend is removed by fitting a local weighted
  #           regression (lowess) to the time series y
  #
  #   ...:    Additional arguments passed to lowess
  #
  # Value:
  # 
  #   Vector with the detrended data.
  #
  # Author:
  #
  #   Caio Coelho <c.a.d.s.coelho@reading.ac.uk> 9 Jan 2006
  # 
  # Examples:
  #
  #      ts <- rnorm(100,25,2)
  #      detrend(ts)
  #      detrend(ts,smooth=TRUE)
  #      detrend(ts,smooth=TRUE,f=1/3)

if(!smooth){
x<-seq(1:length(y))
lm(y ~ x)$res
}
else{
y-lowess(y,...)$y
}
}