I have data of several patients with several observation points. At each observation points we test if the patient has a condition (0) or not (1). I want to perform survival analysis on this data but I'm confused on how to represent the output correctly.
Example data could be:
| Patient | Day | Condition |
-----------------------------
| A | 30 | 0 |
| A | 60 | 1 |
| A | 90 | 1 |
| B | 80 | 0 |
| B | 200 | 0 |
| C | 0 | 1 |
Checking other similar questions such as this or this one I got to
| Patient | Output |
----------------------
| A | (?) |
| A | (30, 60] |
| A | (?) |
| B | (80, NA) |
| B | (200, NA) |
| C | (NA, 0) |
which I don't know if it is correct. Also, how would we represent the observation with a (?)?
What confuses me the most is the fact that the patients have a different number of observations and they are measured at non-regular points. In this fashion I selected as "Day 0" the date of the first observation of all the patients. However, if a patient has the condition on its first observation (lets say day 10) I don't think it is correct to code it as (0, 10) but rather (NA, 10).
Any help would be appreciated.