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st: Re: RE: Re: eliminate negative values and their positive counterpart
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From |
"Sergiy Radyakin" <[email protected]> |
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To |
<[email protected]> |
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Subject |
st: Re: RE: Re: eliminate negative values and their positive counterpart |
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Date |
Tue, 6 Mar 2007 22:53:10 +0100 |
Sorry, (my mistake) this line should be simply omitted. Both npos and nneg
are defined later on.
I guess the solution proposed by Mr Blasnik will exclude observations if the
sum
over a group is zero, but should it be a necessary condition?
30
-30
30
(with all other variables being same) -- e.g. bought apples for 30, than
returned them to the cashier, than decided to buy them again :)
This should simplify to 30, but the sum over the group is not 0.
it is a pity that I can't do as I have written, i.e. -count if- after -egen-
Sincerely yours,
Sergiy Radyakin
----- Original Message -----
From: "Nick Cox" <[email protected]>
To: <[email protected]>
Sent: Tuesday, March 06, 2007 10:20 PM
Subject: st: RE: Re: eliminate negative values and their positive
counterpart
I stopped at this line. There is a typo there
somewhere, as the code is illegal:
by t abs_charge:egen npos=count if charge>0
Nick
[email protected]
Sergiy Radyakin
you will get a dozen of ways to do this more efficiently in
several minutes,
but here is a straightforward way:
Assume your data is:
+------------+
| t charge |
|------------|
1. | 1 10 |
2. | 2 20 |
3. | 2 20 |
4. | 3 30 |
5. | 3 20 |
|------------|
6. | 3 -30 |
7. | 3 -30 |
8. | 4 10 |
9. | 4 20 |
10. | 4 30 |
|------------|
11. | 4 40 |
12. | 5 10 |
13. | 5 20 |
14. | 5 -10 |
15. | 5 -10 |
|------------|
16. | 5 10 |
17. | 5 10 |
18. | 5 20 |
19. | 5 10 |
20. | 5 10 |
|------------|
21. | 5 10 |
22. | 5 -10 |
23. | 5 20 |
24. | 5 -20 |
+------------+
Then
gen abs_charge=abs(charge)
sort t abs_charge
by t abs_charge:egen npos=count if charge>0
gen posit=1 if charge>0
gen negat=1 if charge<0
by t abs_charge:egen npos=count(posit)
by t abs_charge:egen nneg=count(negat)
by t abs_charge:gen ndel=npos*(npos<nneg)+nneg*(nneg<npos)
by t abs_charge:drop if _n<ndel | _n>_N-ndel
Or something similar? change t as appropriate to define a group.
sara borelli
> This is an exctract of my data:
>
> personid charge proc date
> 1000124 +13 80048 6/6/2001
> 1000124 +13 80076 6/6/2001
> ...
> 1000124 +13 80048 6/7/2001
> 1000124 +13 80076 6/7/2001
> ...
> 1000124 -13 80048 6/7/2001
> 1000124 -13 80076 6/7/2001
> ...
> 1000124 +13 80048 6/8/2001
> ...
> 1000124 +13 80048 6/9/2001
> ...
> 1000124 +13 81001 6/11/2001
> ...
> 1000124 +13 80048 6/11/2001
> 1000124 +13 80048 6/12/2001
>
> where the dots indicate that other values for the same
> personid are in between. I need to eliminate the
> negative charges AND their positive counterpart with
> the same proc and date. Thus, for example I need to
> eliminate the negative
> -13 80048 6/7/2001
> AND its positive counterpart with the same proc and
> date:
> +13 80048 6/7/2001,
> and so on.
> I should find a way to construct an algorithm that
> identifies and eliminates the negatives AND their
> poistive counterpart with he same date and procedure,
> but I cannot figure that out.
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