# Re: st: cumulative average moving through time

 From "Michael Blasnik" To Subject Re: st: cumulative average moving through time Date Wed, 6 Oct 2004 16:31:55 -0400

see -help functions- for the very long list of available functions.  The sum
function calculates a cumulative sum for each observation, within each by
group (the by varlist Not in parentheses).  For egen, sum calculates a
constant within by group equal to the sum for that entire group.

Michael Blasnik
michael.blasnik@verizon.net

----- Original Message -----
From: "Daniel Egan" <dp.egan@gmail.com>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, October 06, 2004 3:59 PM
Subject: Re: st: cumulative average moving through time

> Hi Scott,
>
> by sort pid (ob):gen cave = sum(calc)/ob
>
> This is so obvious as to be painful. So why didn't I think of it?
>
> 1) Where/When did -sum()- become an acceptable argument to
> -generate-!?!? I have only ever seen it in the context of -egen-.
> Looking at the help for -generate-, there are no arguments that are
> explicitly stated to be useable. It is only at the very bottom of the
> examples that one sees an function -uniform-  and then -sum- used with
> gen. Are the others?  I know that using many egen arguments with -gen-
> will return errors (e.g. count).
>
> 2) Why does the ---bys pid (ob)-- do this correctly? I understand that
> it is equivalet to --sort PID OB--, but why does it result in the
> correct cumulative sum?
> Another way of putting this is why doesnt -egen cave=sum(calc)/ob,
> by(PID OB)- work if this does?
>
>
> Oh, and thanks. I did not get to try Dan Lawson's code.
>
> Dan Egan

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