Survival analysis t, t0, _d missing at baseline

[Roshani Patel]

Dear Stata community,

When I declare the data to be survival data, I do not know how to specify that time0 is pouchage_days = 0 so that the first observation for each patient is the baseline covariates (thus it should have _t0 = 0 and _t equals the next observation time in days for each patient). In example, there are no entries for _d, _t, and t_0 in baseline row however. Do no know why this is, please help in how to populate these correctly when designating survival options to Stata.

This is the command I have used.

stset pouchage_days, id(id) failure(advanced_adenoma==3) origin(observation==1) scale(1)

Thank you so much for your help.

BW

Roshani

* Example generated by -dataex-. To install: ssc install dataex
clear
input float observation int id float(advanced_adenoma pouchage_days) byte(_st _d) int(_t _t0)
 1 1 1    0 0 .    .    .
 2 1 2 2671 1 0 2671    0
 3 1 1 3028 1 0 3028 2671
 4 1 1 3518 1 0 3518 3028
 5 1 2 3882 1 0 3882 3518
 6 1 2 4246 1 0 4246 3882
 7 1 . 4284 1 0 4284 4246
 8 1 2 4470 1 0 4470 4284
 9 1 2 4815 1 0 4815 4470
10 1 . 4855 1 0 4855 4815
11 1 2 5051 1 0 5051 4855
12 1 2 5219 1 0 5219 5051
13 1 2 5401 1 0 5401 5219
14 1 2 5590 1 0 5590 5401
15 1 2 5954 1 0 5954 5590
16 1 1 6311 1 0 6311 5954
17 1 2 6675 1 0 6675 6311
18 1 . 6864 1 0 6864 6675
19 1 1 7305 1 0 7305 6864
20 1 2 7753 1 0 7753 7305
21 1 3 8614 1 1 8614 7753
22 1 2 9092 0 .    .    .
23 1 1 9387 0 .    .    .
 1 2 1    0 0 .    .    .
 2 2 1 1033 1 0 1033    0
 1 3 1    0 0 .    .    .
 2 3 .  643 1 0  643    0
 3 3 1 1585 1 0 1585  643
 4 3 1 2088 1 0 2088 1585
 5 3 1 2684 1 0 2684 2088
 6 3 1 3422 1 0 3422 2684
 7 3 1 3783 1 0 3783 3422
 8 3 1 4149 1 0 4149 3783
 9 3 1 4513 1 0 4513 4149
10 3 1 5290 1 0 5290 4513
11 3 2 5794 1 0 5794 5290
12 3 2 6620 1 0 6620 5794
13 3 2 7208 1 0 7208 6620
14 3 1 7464 1 0 7464 7208
15 3 2 7691 1 0 7691 7464
 1 4 1    0 0 .    .    .
 2 4 1 5085 1 0 5085    0
 3 4 1 6198 1 0 6198 5085
 4 4 1 6609 1 0 6609 6198
 5 4 2 6994 1 0 6994 6609
 6 4 1 7203 1 0 7203 6994
 7 4 1 7609 1 0 7609 7203
 8 4 2 8095 1 0 8095 7609
 1 5 1    0 0 .    .    .
end

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