cuiliweibj (please don't send HTML!)
> Now here is my data,
>
> . list t1 t2 p12 p21
>
> +---------------------------------------+
> | t1 t2 p12 p21 |
> |---------------------------------------|
> 1. | 884926 115074 .3470322 .1175582 |
> 2. | . . .3154392 .137751 |
> 3. | . . .2806379 .1431388 |
> 4. | . . .2409214 .1699163 |
> 5. | . . .1775456 .2156969 |
> |---------------------------------------|
> 6. | . . .1161977 .2085497 |
> 7. | . . .1420289 .2278323 |
> 8. | . . .1545061 .1971488 |
> 9. | . . .1151673 .2456649 |
> 10. | . . .0701624 .1987177 |
> |---------------------------------------|
> 11. | . . .0555115 .2351439 |
> 12. | . . .0643219 .215013 |
> 13. | . . .0767569 .1852408 |
> +---------------------------------------+
>
>
> In order to get what I want, I did this.
>
> . replace t1=t1[_n-1]+t2[_n-1]*p12[_n-1] if _n>1
> (1 real change made)
>
> . replace t2=t2[_n-1]+t1[_n-1]*p21[_n-1] if _n>1
> (2 real changes made)
>
> . list t1 t2 p12 p21
>
> +-------------------------------------------+
> | t1 t2 p12 p21 |
> |-------------------------------------------|
> 1. | 884926 115074 .3470322 .1175582 |
> 2. | 924860.4 219104.3 .3154392 .137751 |
> 3. | . 346504.8 .2806379 .1431388 |
> 4. | . . .2409214 .1699163 |
> 5. | . . .1775456 .2156969 |
> |-------------------------------------------|
> 6. | . . .1161977 .2085497 |
> 7. | . . .1420289 .2278323 |
> 8. | . . .1545061 .1971488 |
> 9. | . . .1151673 .2456649 |
> 10. | . . .0701624 .1987177 |
> |-------------------------------------------|
> 11. | . . .0555115 .2351439 |
> 12. | . . .0643219 .215013 |
> 13. | . . .0767569 .1852408 |
> +-------------------------------------------+
>
>
> But this is not what I want, I want all the t1 and t2 replaced.
> I tried this, but it doesn't work.
>
> while _n>1 {
> replace t1=t1[_n-1]+t2[_n-1]*p12[_n-1]
> replace t2=t2[_n-1]+t1[_n-1]*p21[_n-1]
> }
>
No, that won't work. One reason alone is that
as far as Stata is concerned each statement
within the loop remains identical. Another
is that although
while _n > 1 {
...
}
makes sense to Stata, you will never get
this loop started because _n by itself
will be interpreted as _n _for the first
observation_ which is 1, so the loop is
while 1 > 1 {
...
}
and thus will never be entered. At least
that's my guess. A related problem is discussed at
http://www.stata.com/support/faqs/lang/ifqualifier.html
This should be closer to what you want:
forval i = 2/13 {
replace t1=t1[_n-1]+t2[_n-1]*p12[_n-1] in `i'
replace t2=t2[_n-1]+t1[_n-1]*p21[_n-1] in `i'
}
Nick
[email protected]
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