# calculate variance of fcs(fold changes) for each quantiles of means
# and returns gene names which abs(fcs) > 2*Zscores

# objects
#   means: numeric vector of means
#   fcs: numeric vector of fold changes
#   LAB: names of probes

zscores = function(i){
  qt = quantile(means, c(0:10)*0.1)
  cls = findInterval(means, qt)
  zs = tapply(fcs, findInterval(means, qt), sd)
  sig = which(abs(fcs) > zs[cls]*2)
  plot(means, fcs, ylim=c(-1,1), pch=16, cex=0.6)
  points(means[sig], fcs[sig], ylim=c(-1,1), col=2, pch=16, cex=0.6)
  return(LAB[sig])
}