Re: st: eliminate oppositie positive and negative values

["Michael Blasnik" <michael.blasnik@verizon.net>]

Woops, I copied your own syntax errors below.  Clearly, yoiu can't have a 
variable named abs(xm) and the code should be changed to absxm.  Also, I would 
combine replace todrop line in with the gen todrop line as one logical 
condition, since it should be faster that way, especially if you are working 
with a large dataset and many times though the loop.

Michael

----- Original Message ----- 
From: "Michael Blasnik" <michael.blasnik@verizon.net>
To: <statalist@hsphsun2.harvard.edu>
Sent: Thursday, March 29, 2007 8:32 AM
Subject: Re: st: eliminate oppositie positive and negative values



> That wouldn't work because there could be offsetting charges and non 
> offsetting charges on the same date so the sum wouldn't be zero.
>
> Although there may be better ways to do this,  to repeat the loop until there 
> is nothing to change you can  use while loop that continues based on a test.
>
> gen abscharge=abs(charge)
> gen abs(xm)=abs(xm)
> local go=1
> while `go' {
> bysort personid proc date abscharge abs(xm)(charge) :
> gen byte todrop=charge!=charge[_n-1] & _n>1
> bysort personid proc date abscharge absxm (charge) :
> replace todrop=1 if charge!=charge[_n+1] & _n<_N
> qui count if todrop==1
> if r(N)==0 local go=0
> drop if todrop==1
> drop todrop
> }
>
>
> Michael Blasnik
>
> ----- Original Message ----- 
> From: "Ron�n Conroy" <rconroy@rcsi.ie>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Thursday, March 29, 2007 5:11 AM
> Subject: Re: st: eliminate oppositie positive and negative values
>
>
>
> > On 29 M�rta 2007, at 02:41, sara borelli wrote:
> >
> > > I need to drop the negatives and the positives with
> > > the same date abs(charge) abs(xm) proc personid. As
> > > suggested by Michael Blasnik in a previous e-mail I
> > > runned the following:
> > doesn't that mean that the charges for a given date should sum to zero?
> >
> > If that's the case then can't you just sum the charges within each  person 
> > within each date and check if they are zero?
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