Calculating the mean

[CEdward]

Hello,

Suppose I have data as follows:

. list , clean
id s_htdate s_testdate cvd
1. 1 3/23/1992 12/30/2003 0
2. 1 3/23/1992 5/12/2004 0
3. 1 3/23/1992 5/13/2004 0
4. 1 3/23/1992 7/19/2004 1

How would I go about calculating the average time that it took before individuals developed CVD given that I am interested in the time between the htdate and the first occurence of cvd? I am interested only in those who developed CVD and its based on multiple record data.

[Nick Cox]

This is answerable by studying various Stata FAQs. How can I identify first and last occurrences systematically in panel data?

http://www.stata.com/support/faqs/da...t-occurrences/ How can I generate a variable containing the last of several dates?

http://www.stata.com/support/faqs/da...ing-last-date/
(This also covers the first date too.)

(The Statalist FAQ does advise looking through the Stata FAQs before posting.)

But there are several ways of doing it. Here's another:

It sounds as if you want

 
bysort id : egen diagnosis_date = min(s_testdate / cvd) 
gen develop_time = diagnosis_date - s_htdate

To average across patients,

 
egen tag = tag(id)
su develop_time if tag, detail