.-
help for ^coding^                                                  (STB-58: sxd2)
.-

Orders the strata formed by different levels of dependent variable
and first stage covariates
-------------------------------------------------------------------------

  	^coding^ depvar [first stage vars] 


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

The @coding@ function orders the strata formed by different levels of
the dependent variable and first stage covariates. This is the order
in which the vector of first stage sample sizes or prevalences
must be entered before calling @msnprev@, @optfixn@, @optbud@ and @optprec@.

The @coding@ function creates a variable called ^grp_yz^ which contains
the distinct groups formed by different levels of the dependent 
variable (Y) and first stage covariates (Z). A list is returned by
@coding@ indicating the definition of each stratum. For calls to
@msnprev@, @optfixn@, @optbud@ and @optprec@, the first-stage sample 
sizes or prevalences must be entered following the order of ^grp_yz^. 


Example
--------
As an illustration, we provide the pilot data described in Table 1
of Reilly (Am. J. Epi, 143, 92-100, 1996):

 . ^use pilotcas^

 . ^coding mort sex^ [get the different strata formed by levels of
	 	    dependent variable (mort) and first stage
	 	    covariates (sex)]

  
gives the output:

 ============OUTPUT OF CODING FUNCTION============

   grp_yz      mort       sex      grp_z       nobs 
        1         0         0          1         25  
        2         0         1          2         25  
        3         1         0          1         25  
        4         1         1          2         25  
for functions requiring first stage sample sizes/prevalences
enter these in the order of grp_yz
============END OF CODING FUNCTION===============


Author
------

      	Marie Reilly, Dept. of Epidemiology & Public Health
	and
	Agus Salim, Dept. of Statistics,

	University College Cork, Cork, Ireland
	marie.reilly@@ucc.ie


Also see
--------

    STB:  STB-58: sxd2
 Manual:  [R] logit, glm
On-line:  help for @logit@, @glm@, @msnprev@, @optfixn@, @optbud@, @optprec@