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Re: st: Recency Weighted cumulative exposures
From
Sergiy Radyakin <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: Recency Weighted cumulative exposures
Date
Wed, 13 Nov 2013 17:23:53 -0500
Carmine, no loops are really necessary:
do http://radyakin.org/statalist/2013111301/recencyw.do
Hope this helps, Sergiy Radyakin
On Wed, Nov 13, 2013 at 5:08 PM, Carmine Rossi, Mr
<[email protected]> wrote:
> Dear STATA listers,
>
> I have the following repeated measures data on two subjects with a dose exposure variable. I am interested in creating a variable called “result” that is a recency-weighted cumulative sum.
>
> id time dose result
> 1 1 0 0
> 1 2 0 0
> 1 3 2.6 2.6
> 1 4 2.6 5.174
> 1 5 3.2 8.218
> 2 1 0 0
> 2 2 0 0
> 2 3 0.7 0.7
> 2 4 0.7 1.393
>
> The “result” variable is obtained as a cumulative sum using a weight function:
> Summation of (Dose(i) x weight(t)), where the weight function is:
>
> W(t) = exp((-(delta time)2)/70.70)
>
> So to get the weighted cumulative sum value of 8.218 (for subject 1 at time 5), rather than 8.4, which would have been the un-weighted cumulative sum, I did the following in a spreadsheet.
>
>
> Id time dose delta_t w(t) dose(t)*weight(t) cumulative_sum
> 1 1 0 4 0.80 0 0
> 1 2 0 3 0.88 0 0
> 1 3 2.6 2 0.94 2.444 2.444
> 1 4 2.6 1 0.99 2.574 5.018
> 1 5 3.2 0 1 3.2 8.218
>
> Is there a way to do this in STATA with loops? Can anyone provide any suggestions?
>
>
> Carmine Rossi
> PhD Candidate, Epidemiology
> McGill University
> [email protected]
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