Re: st: eliminate oppositie positive and negative values

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

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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