Re: st: Re: eliminate negative values and their positive counterpart

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

Here's one way to only drop matched pos/neg pairs:

gen abscharge=abs(charge)
bysort personid proc date abscharge (charge) : gen byte 
todrop=charge!=charge[_n-1] & _n>1
bysort personid proc date abscharge (charge) : replace todrop=1 if 
charge!=charge[_n+1] & _n<_N
drop if todrop==1
drop todrop

You would need to run this more than once if there are multiple matched 
pos/beg pairs with the same values.  The hasnegative var is superfluous for 
this approach since the only way that charge!=charge[_n-1] within the same 
abscharge is if they differ in sign.

Michael Blasnik


----- Original Message ----- 
From: "sara borelli" <saraborelli77@yahoo.it>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, March 07, 2007 12:37 PM
Subject: Re: st: Re: eliminate negative values and their positive 
counterpart



> Hi Michael,
>
> I am sorry to write again about the question of
> yesterday
> I am not sure how I would change the code you
> suggested in the following case:
>
> claimnum   personid  servdate     charge     proc
> 4087      1000124    2001-06-06   +25274.25   121
> 4510      1000124    2001-06-06   -25274.25   121
> 4511      1000124    2001-06-06   +25274.25   121
>
> If I want to eliminate the negative charge AND both
> positive counterparts I just type drop if
> hasnegative==1.
>
> The problem is that I might need to drop the negative
> and only one of the positive counterparts, but the
> only variable that can distinguish between the two
> positives is claimnum, which cannot be used to define
> a group since it is unique to each observation
>
> thank you in advance
> Sara
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