R/ttest.func.R

In lpc: Lassoed Principal Components for Testing Significance of Features

ttest.func <- function(x,y,s0=0, sd=NULL){
  n1 <- sum(y==1)
  n2 <- sum(y==2)
  p <- nrow(x)
  m1 <- rowMeans(x[,y==1,drop=F])
  m2 <- rowMeans(x[,y==2,drop=F])
  if(is.null(sd)){
    sd <- sqrt( ((n2-1) * varr(x[, y==2], meanx=m2) + (n1-1) * varr(x[, y==1], meanx=m1) )*(1/n1+1/n2)/(n1+n2-2) )
  }
  numer <-  m2 - m1
  dif.obs <- (numer)/(sd + s0)
  return(list(tt=dif.obs,numer=numer, sd=sd))
}