Hi

I need some help with Stata syntax. I have a dataset with persons who have participated in a health survey, and later had a specific surgery, aprox. 1000 persons and 650 variables. The health surveys have been performed every 5-10 years from 1970 to 2018, a total of 7 times. Each survey has about 100 variables. The persons have participated in between 1 and 7 surveys. The dataset is organised like this:

ID date1 height1 weight1 bloodpressure1 ....... date2 height2 weight2 bloodpressure2 ........ date3 height3 weight3 bloodpressure3 ...[....] date7 height7 weight7 ...... date_of_surgery

For each person, I want to perform analyses on the variables from the survey closest to date of surgery (before surgery, not after). How do I transform my dataset to select only those variabels? Date of surgery is sometimes between surveys, sometimes after the last survey.

I am grateful for any tips.