st: missing events in stset

[Sara Mottram <s.mottram@cphc.keele.ac.uk>]

Hi,

I am having some difficulty with -stset-. I'm almost certain that the 
fault lies with my data, as this same command has worked before in a 
similar dataset. However, I wonder if anyone could give me an idea as to 
where I might start looking to find the problem.

I have long data, identified by a variable surveyid. An event is a 
consultation with a doctor (kcons_post_3yr==1). Each person enters at 
their clinical assessment (edateass) and leaves at their censor time 
(censor_date). I know from a tabulation of the data that there are 734 
consultations, but when I use -stset- it identifies 730 events. One 
person consults at time 0, so I think this person is being ignored - I 
understand this. However, this still leaves three events that are 
unidentified.

I have 742 people in the dataset so it is including everyone and I have 
checked that these consultations are not occurring after the censor 
date, so I don't think this is the problem. Also, I have checked that 
there are no missing values in any of the variables in the -stset- command.

Is there anything else that could obviously be causing this problem?

Best wishes
Sara


stset cons_dt, id(surveyid) fail(kcons_post_3yr==1) origin(time 
edateass) exit(time censor_date)

             id:  surveyid
  failure event:  kcons_post_3yr == 1
obs. time interval:  (cons_dt[_n-1], cons_dt]
exit on or before:  time censor_date
 t for analysis:  (time-origin)
         origin:  time edateass

------------------------------------------------------------------------------ 
 16704  total obs.
    28  obs. end on or before enter()
------------------------------------------------------------------------------ 
 16676  obs. remaining, representing
   742  subjects
   730  failures in multiple failure-per-subject data
703420  total analysis time at risk, at risk from t =         0
                          earliest observed entry t =         0
                               last observed exit t =      1096

--
Sara Mottram	
Research Assistant: Biostatistics
Primary Care Musculoskeletal Research Centre
Primary Care Sciences
Keele University
Staffordshire, ST5 5BG
Tel:  	+44 (0) 1782 584711
Fax:  	+44 (0) 1782 583911
Email:	s.mottram@cphc.keele.ac.uk

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