Hi all,

I'm not a frequent Stata user and got stuck on something that I think ought to be fairly simple. Perhaps someone here could help? I'm using Stata 16.0.

I'd like to calculate associations (using Spearman's rank correlation) between different biomarkers that are measured within 60 days from each other. I have panel data with 10 biomarkers, some measured only once and some up to four times, and some are measured the same date and some not (see data below(I only included two biomarkers to make it simpler)). How can I make this calculation across rows? I assume I need to get biomarker1 to populate the same row as biomarker2 if the id is the same and the biomarker_date is within 60 days, but I don't understand how. Does anyone know?

Many thanks!

Best
Gunnar



Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float id double biomarker_date float(biomarker1 biomarker2)
185              21805         .  772.1053
117              21815         .  386.8421
248              21910         .       280
191              20135         .  303.1579
273              20381         .  320.5263
273              20167         .  283.6842
265              20275         . 174.73685
124              20290         .  652.6316
258              20891         .         .
258              20891         . 35.789474
258  20891.57986111111         .         .
258              21231         .  39.47368
258              20986         .         .
258  21231.48611111111         .         .
258              21231         .         .
258              20986         .         .
258              21231         .         .
258              20986  6.481458         .
258              20891         .         .
250         20954.5625         .         .
250              20520  11.93801         .
250              20954         .         .
250              20520         .         .
250              20954         .         .
250              20520         .         .
250              20520         .  461.0526
250              20520         .         .
250 20520.583333333336         .         .
250              20954         .  362.6316
250              20520         .         .
250              20954         .         .
173              21223         . 111.05264
173              21223         .         .
173              21223         .         .
173              21223         .         .
173              20849         .         .
173 20544.479166666664         .         .
173              20849         . 168.21053
173              20849   2.76059         .
173              21223  3.469453         .
173              20849         .         .
173              20508         .         .
173              20544         .         .
173  21223.46527777778         .         .
173              20557         .   83.1579
173              20849         .         .
173              20544         .         .
173              20849         .         .
173              20508         .         .
173              20508 3.8420894         .
173              21223         .         .
173              21669         . 137.89473
190              20213         .  673.6842
206              20053         . 361.57895
214              20282         .  412.6316
169              20242         . 331.57895
197              20968         .         .
197              21600         . 151.57895
197              20943         .         .
197              21600         .         .
197              21293 14.454144         .
197              20943         . 194.21053
197              21293         .         .
197              20968 14.237902         .
197              21293         . 227.36842
197              20943         .         .
197 21293.458333333336         .         .
197              21293         .         .
197  20943.59027777778         .         .
197              21293         .         .
197              21600         .         .
197              21293         .         .
197              20968         .         .
158              20107         . 110.52631
225              20178         . 201.57895
261              19935         .  726.3158
133              20787         .         .
133 21171.583333333336         .         .
133              20787         . 431.57895
133              21171         .  673.6842
133              21076         .         .
133              20559 18.342129         .
133              20559         .         .
133              21171         .         .
133 20787.583333333336         .         .
133              20787         .         .
133              21171         .         .
133              20559         .         .
133              21076         .         .
133              21076  38.20453         .
133              20256         .  213.1579
123              20555  18.10814         .
123              20790         .         .
123              21068         .         .
123              20888 22.946787         .
123              20888         .         .
123              20790         .         .
123              20555         .         .
123              20888         .         .
123              21068  27.05924         .
end
format %td biomarker_date