Thanks Sven,
Just a couple of questions.

If you do element-by-element operations, I don't see any reason to
expect higher speed.

Ok, it does make sense! But instead, why does it seem to be so much slower ?

Plus, in this case you're mixing series (x) and
matrices (example2). My speculation would be that it's slower because
gretl has to figure out what you want to do and if that's really
syntactically correct.

That's a very good point I did miss 8-) .
But I tried with the following script
    matrix example2 = x
    matrix example3 = zeros($nobs,1)
    loop for i = 1..$nobs --quiet
        example3[i,1] = example2[i,1]
    endloop
and this still remains much slower than series operation (even though faster then the previous mixing)

Cheers,
artur