Hello, This is just for discussion. I used to think that in doing mathematical calculations, the matrices need not to be mixed up with series. For the sake of clarityone can not, let's say multiply a series by a matrix. Is that right? Well, in the following script this kind of multiplication works fine. Is that normal -- I mean, an intentionnally built feature -- or should we avoid such a mixed operation? nulldata 100 series x1 = normal() matrix unit = ones($nobs,1) scalar prod = unit'*x1 # matrix * series matrix mx1 = x1 scalar prod = unit'*mx1 # matrix * matrix best, artur