On Thu, 7 Nov 2013, antonio.puca(a)enel.com wrote: Two nearly equivalent methods (they only differ in the way you define standard deviation, really): <hansl> nulldata 700 setobs 7 2012-01-01 series x = normal() period = $obsminor + ($obsmajor - min($obsmajor))*12 # -------- method 1 --------------------------------- matrix m = aggregate(x, period, mean) matrix s = aggregate(x, period, sd) series mm = replace(period, m[,1], m[,3]) series sm = replace(period, s[,1], s[,3]) series z1 = (x - mm)/sm # -------- method 2 --------------------------------- ols x const dummify(period) --quiet series w = $uhat series w2 = w*w ols w2 const dummify(period) --quiet series s2 = $yhat series z2 = w / sqrt(s2) </hansl> ------------------------------------------------------- Riccardo (Jack) Lucchetti Dipartimento di Scienze Economiche e Sociali (DiSES) Università Politecnica delle Marche (formerly known as Università di Ancona) r.lucchetti(a)univpm.it http://www2.econ.univpm.it/servizi/hpp/lucchetti -------------------------------------------------------