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help for pairdata
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Create paired datasets from individual-per-row data

    Basic syntax:

        pairdata varlist [if exp], individual(varname) family(varname)
                     [constant(varlist)]


Description

    pairdata converts individual-per-row data to single and double-entered
    paired data.


                                 (original)           


                             fam        ind     var     cons
                        -------------------------------
                                   1    1       44      P
                                   1    2       45      P
                                   1    3       46      P
                                   2    1       47      Q
                                   2    2       48      Q



                                  (single)           


                      fam       cons    ind_1   ind_2   var1_1  var1_2
              ---------------------------------------------------
                                 1      P       1       2       44      45
                                 1      P       1       3       44      46
                                 1      P       2       3       45      46
                                 2      Q       1       2       47      48



                                  (double)           

                      fam       cons    ind_1   ind_2   var1_1  var1_2
              ---------------------------------------------------
                                 1      P       1       2       44      45
                                 1      P       1       3       44      46
                                 1      P       2       3       45      46
                                 1      P       2       1       45      44
                                 1      P       3       1       46      44
                                 1      P       3       2       46      45
                                 2      Q       1       2       47      48
                                 2      Q       2       1       48      47


    pairdata creates three paired datasets based on pair combinations within
    familyID:

        double.dta: double entered file with all possible pair combinations
        single.dta: single entered file with unique pair combinations
        singlerand.dta: single entered file with unique pair combinations
            controlling for any type of order effect



    pairdata also generates two new variables for each of the three files:


        famcount: the number of members in each family.
        nsibpair: a count of the number of pairs formed from each family.



Required Options

    individual(varname) Specify individualID variable, this must be numeric
        and unique within familyID.

    family(varname) Specify familyID variable, this must be numeric and
        unique between families.


Other Option

    constant(varname) Specify constant variables, i.e. family specific
        variables.


Examples

. pairdata var1 var2, ind(individualID) fam(familyID)
. pairdata var1-var2, ind(individualid) fam(familyid) con(famtype)


Author

        Richard J Williamson.
        Social Genetic Developmental Psychiatry Research Centre,
        Institute of Psychiatry,
        Kings College London.
        U.K.
        richard.williamson@iop.kcl.ac.uk