re: Re: st: Running Product Function

[Christopher Baum <kit.baum@bc.edu>]

<>
Yuval said

by appt: replace reduct_per=1 if reduct_per==0
by appt: gen y1=exp(sum(ln(reduct_per)))

Note that the first command need not be run under by-control.
On my machine, on a panel of ~18k obs, this runs about twice as fast:

by appt: gen y1=exp(sum(ln(cond(reduct_per==0, 1, reduct_per))))

Also note that in working with log() and exp() it would be a good idea to use doubles in the computation.

KIt

Kit Baum   |   Boston College Economics & DIW Berlin   |   http://ideas.repec.org/e/pba1.html
                             An Introduction to Stata Programming  |   http://www.stata-press.com/books/isp.html
  An Introduction to Modern Econometrics Using Stata  |   http://www.stata-press.com/books/imeus.html


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