[R] question about survSplit

From: singyee ling <singyee.ling_at_googlemail.com>
Date: Thu 18 May 2006 - 01:00:56 EST


Dear R-users,

I use the survsplit function in the survival package to change my data into counting-process format

and the transformed format is as follow:

(a)

start stop event DP age ....

0      5         0        1       20
5     10        0        1       20
10    25       1        1       20


looking at the above three entries that belong to the same person, if an event happen at time 5, won't the person actually enter the risk set twice since there is another entry that start at time 5 and Cox proportional hazard model "won't know" that it actually belong to the same person.

Shouldn't it be like this?

(b)

start stop event DP age ....

0      5         0        1       20
6    10         0        1       20
11   25        1        1       20

or the R-function coxph has already take this into account when calculating its risk set although I believe (a) is actually the correct one. Your advice is greatly appreciated!

regards,
sing yee

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