Hi STATA users,

I have a set of survival data as below which is from a longitudinal study. And I know that 6 out of 50 are not failures in the last visit.

I am wondering why the survival function at 26.5 is missing.

Also, at about 26 months, the curve drops to zero. Which might look like the accumulated success rate is 0. I can understand that is because some of the participants are censored since the survival time is less than 26 months which is the last subject that has a failure.

I am considering how to deal with this situation for a longitudinal study.

Thank you.







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Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input double maindemographicid byte(_st _d _t0) double _t
 38 1 1 0 .46052631578947373
 74 1 1 0  .8223684210526316
111 1 1 0  .8223684210526316
149 1 1 0  .8552631578947368
 84 1 1 0  .8881578947368421
 87 1 1 0  .8881578947368421
 48 1 1 0  .9210526315789475
119 1 1 0  .9210526315789475
 89 1 1 0  .9210526315789475
125 1 1 0  .9210526315789475
 82 1 1 0  .9210526315789475
 72 1 1 0  .9210526315789475
113 1 1 0  .9210526315789475
 56 1 1 0  .9539473684210527
114 1 1 0  .9539473684210527
 46 1 1 0 1.0197368421052633
158 1 1 0 1.0197368421052633
147 1 1 0 1.0855263157894737
 76 1 1 0 1.1513157894736843
 63 1 1 0 1.1513157894736843
 29 1 1 0 1.1513157894736843
102 1 1 0 1.1842105263157896
122 1 1 0 2.2039473684210527
150 1 1 0 2.6644736842105266
106 1 1 0  2.763157894736842
 26 1 1 0 2.7960526315789473
109 1 1 0 2.8947368421052633
 12 1 1 0 2.9276315789473686
 59 1 1 0  2.993421052631579
108 1 1 0  2.993421052631579
132 1 1 0 3.0263157894736845
126 1 1 0  3.223684210526316
 50 1 1 0 3.4539473684210527
 70 1 1 0 3.7171052631578947
 94 1 1 0 5.7894736842105266
 67 1 1 0  5.855263157894737
 52 1 1 0               6.25
155 1 1 0 11.447368421052632
137 1 1 0 11.743421052631579
136 1 1 0             11.875
156 1 1 0  13.55263157894737
123 1 1 0 18.585526315789476
 69 1 0 0 22.697368421052634
104 1 0 0              23.75
 16 1 1 0  23.88157894736842
 77 1 0 0  24.17763157894737
 45 1 0 0 24.342105263157897
 61 1 0 0 24.572368421052634
 99 1 0 0  24.80263157894737
140 1 1 0  26.48026315789474
end


sts list,  at(1 3 6 12 18 24 26.5 )


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