Cumulative product over a variable

[Isabel Lechner]

Hi

I am trying to calculate the cumulative product of a variable (var1) and get the result in a new variable (product). Example:

var1 product
1 1
3 3
5 15
7 105

Any ideas on how to best implement this in Stata 15.1? Thanks!

[Clyde Schechter]

clear*
set obs 4
gen var1 = 2*_n - 1
list, noobs clean

gen product = 1 in 1
replace product = product[_n-1]*var1 in 2/L

list, noobs clean

[Carlo Lazzaro]

Isabel:
as an aside to Clyde's helpful reply, I recall an old trick proposed by Nick that saved my head from an urgent TC scan after having banged it against the wall all the afternoon long some years ago:

. set obs 10

. g A=_n

. g B=sum(ln(A))

. replace B=exp(B)

[Isabel Lechner]

Thank you Clyde, I acutally finally got to the very same solution just a few seconds ago.

[Nick Cox]

It does no harm to insist that products go in double variables.