Dear Gretl Users!
I've 30 variables and want to generate vector (n) with number of valid observations for each variable. I'm using 'ok' function but something is wrong (see script below). Probably '$i' is not taken as an i-th variable but as a series containg only "i". What do you think about it? How to be sure that '$i' is taken as an i-th variable?

<hansl>
n=zeros(30,1)
loop i=1..30
a=sum(ok($i))
n[i,1]=a
endloop
print n

Regards,
Mariusz