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Re: st: Loop-within-loop error while looping over observations for a microsimulation


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Loop-within-loop error while looping over observations for a microsimulation
Date   Mon, 6 Aug 2012 20:45:09 +0100

You still have a problem.

          replace childbirth[_n+j]== .i if (childbirth==1) in `i'

is illegal, as explained.

This kind of statement would be legal

 if (childbirth[<subscript>]  == 1)  replace childbirth = .i in <something>

but I am not certain that it is what you want.

On Mon, Aug 6, 2012 at 8:08 PM, Stephen Cranney
<cranney.stephen@gmail.com> wrote:
> But with the current syntax isn't that not a problem? If I input the
> numbers directly I have the following:
>
> local N = _N
> forvalues i = 1/`N' {
>         forvalues j= 0/12 {
>
>                 replace childbirth= rbinomial(1, probabilityconceive)
> if childbirth== .f
>                 replace childbirth[_n+j]== .i if (childbirth==1) in `i'
>                 }
>         }
>
>
> Here 1/`N' is directly computed before the loop starts, and the j
> values are inputted directly (with the higher bound being the number
> of postpartum months), so I'm still not seeing exactly how the syntax
> has a problem. I've closed off the space that was between childbirth
> and the _n, so it's not that it's accidentally recognizing the value
> as a weight.
>
> Thanks,
>
> Stephen
>
> On Mon, Aug 6, 2012 at 11:59 AM, Nick Cox <njcoxstata@gmail.com> wrote:
>>
>> No "seems to indicate" here: simply, subscripts are not allowed to the
>> left of the assignment in Stata.
>>
>> The syntax diagram shows the form -replace oldvar = exp-. Stuff can
>> follow that, but nothing else can be included.
>>
>> Nick
>>
>> On Mon, Aug 6, 2012 at 4:53 PM, Stephen Cranney
>> <cranney.stephen@gmail.com> wrote:
>> > Thanks for catching that; it's still giving me the "weights not
>> > allowed" error message though, even when I delete the extra space.
>> >
>> > I found this prior Statlist post that seems to indicate that Stata
>> > triggers the no weights allowed warning when the `i' is placed to the
>> > left of the equals sign:
>> >
>> > http://www.stata.com/statalist/archive/2006-08/msg00976.html
>> >
>> > So I changed my code to the following, but I'm still getting the "no
>> > weights allowed" message.
>> >
>> > local N = _N
>> > forvalues i = 1/`N' {
>> >         forvalues j= 0/12 {
>> >                 replace childbirth= rbinomial(1, probabilityconceive) if childbirth== .f
>> >                 replace childbirth[_n+j]== .i if (childbirth==1) in `i'
>> >                 }
>> >         }
>> >
>> > Best,
>> >
>> >
>> >
>> > On Mon, Aug 6, 2012 at 9:32 AM, daniel klein
>> > <klein.daniel.81@googlemail.com> wrote:
>> >> I did not follow closely, but there is a space between <childbirth>
>> >> and  <[`i']> in your code, probably causing Stata to interpret <[`i']>
>> >> as some kind of weight, rather than a subscript.
>> >>
>> >> Best
>> >> Daniel
>> >>
>> >> --
>> >> [...]
>> >> However, when I change the
>> >> monthsofpostpartum variable to a constant (in this case 12), it's
>> >> giving me a "weights not allowed" sign.
>> *
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