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


From   Stephen Cranney <cranney.stephen@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Loop-within-loop error while looping over observations for a microsimulation
Date   Tue, 7 Aug 2012 09:10:07 -0600

Okay, I so I fixed the problems mentioned. I get an "invalid inXY"
reading the first observation after the first birth and the rest stay
as .f When I run the command with capture I get a series of 1s and 0s
but without any of the postpartum replacements with .i.

local N = _N
local  monthsofpostpartum =  12
forvalues i = 1/`N' {
        forvalues j= 1/`monthsofpostpartum' {
              capture  if childbirth[`i']== .f replace childbirth =
rbinomial(1, probabilityconceive) in `i'
				local k = `i' + `j'
			capture if childbirth[`i']==1 replace childbirth= .i in`k'
                }
        }

On Tue, Aug 7, 2012 at 4:09 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> I am surprised at your syntax
>
> ... in `N'+`j'
>
> as I didn't know that Stata would do the mathematics there. But
> regardless of that, observation `N' + `j' is at position _N + 1 ... _N
> + 12 and so always outside your dataset, so nothing would be done Your
> logic appears to call for
>
> local k = `i' + `j'
> if childbirth[`i']==1 replace childbirth= .i in`k'
>
> I note also that
>
>         if childbirth[`i']== .f replace childbirth= rbinomial(1,
> probabilityconceive)
>
> -replace-s in every observation, including those earlier declared
> times when infertile. That can't be what you intend, so you need to
> specify -in- here too.
>
> That said, I don't see that you need to reach for the exotic machinery
> of extended missing values. Infertility post partum would seem to be
> represented naturally by 0; the value is known and zero, and for a
> specific reason, not unknown for a specific reason.
>
> Nick
>
> On Tue, Aug 7, 2012 at 12:31 AM, Stephen Cranney
> <cranney.stephen@gmail.com> wrote:
>> Thank you all so much, that worked to make the syntax legal. I'm
>> almost there, but it's not quite doing what I want it to. To recap,
>> the data is sorted by year and month. When the "birth" is created out
>> of the binomial function, I want the code to detect it and make a
>> number of the subsequent months "infertile" so that binomial
>> probability of births won't work during those months. .f= fertile
>> missing, .i is missing for after-birth infertility.
>> "monthsofpostpartum" is a local macro that is simply the number of
>> months of after-birth infertility. This just gives me a sequence of 1s
>> and 0s; it doesn't seem to be replacing the subsequent months after
>> birth with the .i
>>
>> local N = _N
>> local  monthsofpostpartum =  12
>> forvalues i = 1/`N' {
>>         forvalues j= 1/`monthsofpostpartum' {
>>                 if childbirth[`i']== .f replace childbirth= rbinomial(1, probabilityconceive)
>>                 if childbirth[`i']==1 replace childbirth= .i in`N'+`j'
>>                 }
>>         }
>>
>> Thanks in advance,
>>
>>
>>
>> On Mon, Aug 6, 2012 at 1:45 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>>> 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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