.-
help for ^stjoin^                                          (STB-45: dm62)
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Joins episodes at which variables are time-constant
---------------------------------------------------

        ^stjoin^ [varlist] [^, eps(^#^)^ ^k^eep]

^stjoin^ is for use with survival-time data; see help @st@.  You must have ^stset^
your data before using this command; see help @stset@.


Description
-----------

^stjoin^ reduces the memory demands and execution time for the analyses of ^st^ 
data by joining episodes E1 and E2 with st-variables (id,t0,t,d) if this can 
be done without loss of information. This is the case if 

  * both intervals belong to the same case (obs with same value of id),
  * episode E1 was not terminated by death (d!=0),
  * all variables in varlist have identical values in E1 and E2, and
  * the exit-time of the episode E1 is right (less that eps) before the 
    entry-time of episode E2

^stjoin^ reports the number of cases (obs with same value of id) affected and 
the number of episodes removed.


Options
-------

^eps(^#^)^ specifies the minimal elapse of time between exit and re-entry so 
    that subsequent episodes are to be counted as sequential. ^eps^ defaults 
    to 0.
    
^keep^ specifies that all variables in the data set are regained. The default 
    behavior of ^stjoin^ is to drop variables that are not included in varlist
    and are not one of the st key-variables (entry times etc).
    
    
Remark    
------

For Cox regression, a further reduction of episodes is possible for larger gaps
between episodes, provided that no event (failure) for any of the other cases 
occured during the gap. Such a modification does not affect the composition of 
risk sets, and hence the partial likelihood. The current version of ^stjoin^ 
does not support this feature.


Example
-------

    . ^stset studytim died^
    . ^stsplit X, every(5)^                      (split in episodes of length 5) 
    . ^stjoin age drug^                           (effectively undoes the split)
    . ^stcox age drug^       
                

Acknowledgment
---------------

This project was supported by research grant PGS 50-370 by the Netherlands 
Organization for Scientific Research.        


Author
------

       Jeroen Weesie
       Utrecht University, Netherlands
       J.Weesie@@fss.uu.nl


Also See
--------

    STB:  dm62 (STB-45)
 Manual:  [R] st
On-Line:  help for @st@, @stsplit@