normalization_wrapper <- function(expr, th = 2.5){
  expr_norm <- apply(expr, 1, function(x){ 
    sdx <- sd(x, na.rm = TRUE)
    if(sdx == 0){
      x <- (x - mean(x, na.rm = TRUE))
    }else{ 
      x <- (x - mean(x, na.rm = TRUE)) / sdx
    }
    x[x > th] <- th
    x[x < -th] <- -th
    return(x)
  })
  expr_norm <- t(expr_norm)
}