# extension for dependent samples pooled standard deviation - 29 Jan 2008 -SylviaDKreibig
# Based on Dunlap, Cortina, Vaslow & Burke, 1996; Cohen, 1988
# absolute (signless) effect size - 31 Aug 2004 -PLH
# This uses Cohen's (1988) p44 pooled variance method.
get.d <- function(x,y,absolute=T, dependent=F){
  if (absolute)  diff <- abs(mean(x,na.rm=T)-mean(y,na.rm=T))
  else diff <- mean(x,na.rm=T)-mean(y,na.rm=T)
  if (dependent)
    S <- sqrt((sd(x,na.rm=T)^2
               +sd(y,na.rm=T)^2
               -2*cor(x,y,method="pearson")
                 *sd(x,na.rm=T)*sd(y,na.rm=T)
               ))
  else S <- sqrt((sd(x,na.rm=T)^2+sd(y,na.rm=T)^2)/2)
  d <- diff/S
  return(d)
}