Dear Statalist members,

I manually constructed duration data for survival analysis. However, I could not be sure whether I followed Stata manual correctly. I'll analyse multiple ordered failure-time data by following this entry: https://www.stata.com/support/faqs/s...me-data/#cond1

Let me compare the example in this entry and my data:

Stata example:

Code:
 +------------------------+
| id time0 time failure size_tumor failure_risk |
|------------------------|
9. | 0 12 1 1 1 |
9. | 12 16 1 1 2 |
9. | 16 18 0 1 3|
+------------------------+
My data with missing observations:

Code:
 +------------------------+
| id time0 time failure size_tumor failure_risk |
|------------------------|
9. | 0 12 1 1 1 |
9. | 14 14 1 1 2 |
9. | 16 18 0 1 3|
+------------------------+

So I don't observe individual 9 all the time and as it is recurrent event I could not get the status of individual in terms of failure (it's not like mortality). My questions:

1) Can I leave data structure as it is shown in here? Or do I need to drop observation like second row where I observed individual only in one check-up.
2) Is it true to define exit and enter as following: exit(time .) enter(time0) or exit is the only last occurrence not exit before the missing observations?
3) What time0=0 means actually? I replace the first observation as 0 while in the original data it's check-up 1, so time0 starts with 1. Does it matters in the Cox model?

Best regards,
John