Collapse function that calculates product

[Daria Fomenko]

Is there a function that does what the collapse function does but calculates the product of the values for the selected variable.

I need it to calculate the yearly return out of monthly returns.

Thank you very much in advance!

[Maarten Buis]

You can take the logarithm of a variable, use collapse to compute the sum of that variable, and than exponentiate that to get the product. The logic is that :

\[
\exp(\ln(a) + \ln(b) + \ln(c)) = \exp(\ln(a \times b \times c)) = a \times b \times c
\]

[daniel klein]

This is clever! Thanks.

[Daria Fomenko]

Thank you so much, Mr Buis!

[Nick Cox]

Duplicate thread at http://www.statalist.org/forums/foru...ulates-product

Please note the request there to use a full real name as identifier.