Re: st: how do i increment a counter

["aine dooley" <acd4983@hotmail.com>]

Thanks so much for taking the time to reply.

You are right, my example wasn't the best.

What I am actually trying to do is loop through a list of 6500 patients. 
Each patient has an exposure_time i.e. the period of time in days during 
which they are at risk for a fracture. For each age category (see below), I 
want to add up a cumulative time at risk. So for ages 51-75, I want to come 
out with a number that contains the total exposure_time for all patient in 
that age category.

I think numlist apparently only allows 1600 observations which is somehow 
incremented by using numlist, max('totobs`) though I haven't figured out the 
syntax.

I'm sure there is a more elegant way to do this, however ...

local age1_sum=0
local age2_sum=0
local age3_sum=0
local age4_sum=0
local totobs = _N

foreach obs of numlist 1/`totobs' {
  if age[`obs']<=50 {
     local age1_sum = `age1_sum' + exposure_time[`obs']
  }
  else if age[`obs'] >50 & age[`obs'] <= 75 {
	      local age2_sum = `age2_sum' + exposure_time[`obs']
  }
  else if age[`obs'] >75 & age[`obs'] <= 90 {
	      local age3_sum = `age3_sum' + exposure_time[`obs']
  }
  else local age4_sum = `age4_sum' + exposure_time[`obs']
}


-Annemarie
University of Washington, Seattle


> From: Christian Holz <statalist@krueschan.de>
> Reply-To: statalist@hsphsun2.harvard.edu
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: how do i increment a counter
> Date: Wed, 31 Aug 2005 21:03:09 +0100
>
> Annemarie,
>
> you should also check the syntax of the if command (-help ifcmd-). The 
> command that you want to be executed if the if statement is true should be 
> either follow on the same line as the "if" or should be enclosed by { }.
>
> That still does not, however, solve the problem, that your code looks quite 
> confused.
> In addition to Neil's interpretations of what you might want to achieve, it 
> might also be to get a sum of the age of all observations in your dataset 
> that are over 50 (assuming your age variable is "age"). In that case you 
> could do
>
> local total_sum=0
> local totobs = _N
>
> foreach obs of numlist 1/`totobs' {
>    if age[`obs']>50 {
>       local total_sum = `total_sum' + age[`obs']
>    }
> }
> di `total_sum'
> generate total_sum=`total_sum'
>
>
> C.
>
> ---
> Christian Holz
> Department of Sociology
> University of Glasgow
> Scotland, U.K.
>
> aine dooley wrote:
>
> > I am finding in Stata that there does not seem to be an easy way to 
> > increment a counter despite countless trys and readings of the manal.
> >
> > I want to do something llike the following, this is just an example:
> >
> > generate byte total_sum =0
> >
> > for each variable of varlist {
> > if age > 50
> >    total_sum = total_sum + age
> > }
> >
> > Stata doesn't seem to allow the if... then construct unless it is in a 
> > program. Although I have written a simple program (crazy that I have to do 
> > this) passing arguments, I still can't get it to work.
> >
> > I must be missing something.
> >
> > -Annemarie
> >
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