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
n.j.cox@durham.ac.uk
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.
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/