Scale data frame with both continuous and binary variables

myscale.R

isBinaryVariable = function(x) {
  apply(x, 2, function(j) {
    return (identical(range(unique(j)), c(0,1)))
  })
}

scaleBinary = function(j) {
  p = mean(j)
  j.sd = sqrt(p*(1-p))
  (j - p) / j.sd
}

myscale = function(x, scale.binary=T, ...) {
  binary = isBinaryVariable(x)
  if (!scale.binary) {
    if ("data.table" %in% class(x)) x[,!binary,with=F] = scale(x[,!binary,with=F], ...)
    else x[,!binary] = scale(x[,!binary], ...)
  }
  else {
    if ("data.table" %in% class(x)) {
      x[,!binary,with=F] = scale(x[,!binary,with=F], ...)    
      x[,binary,with=F] = apply(x[,binary,with=F],2,scaleBinary)
    }
    else {
      x[,!binary] = scale(x[,!binary], ...)
      x[,binary,with=F] = apply(x[,binary,with=F],2,scaleBinary)
  }
  return (x)
}