help joinvars
-------------------------------------------------------------------------------

Title

     joinvars -- Join values of variables

Syntax

        joinvars newvar [=] varlist [if] [in] [, options]

    options                Description
    -------------------------------------------------------------------------
      update               replace non-missing values with non-missing values
      missok               replace non-missing values with missing values
    -------------------------------------------------------------------------

Description

    joinvars creates variable newvar containing joined values of varlist.
    Starting with a copy of the first variable in varlist, missing values in
    newvar are replaced with values of the next variable(s) in varlist.

Options

        +---------+
    ----+ Options +----------------------------------------------------------

    update replaces non-missing values in newvar with values of variables in
        varlist. Default is to replace missing values only.

    missok replaces non-missing values in newvar with missing values of
        variables in varlist. May only be specified with update.

Example

    First, I separate wages by race in the NLSW 1988 dataset using separate.

        . sysuse nlsw88 ,clear
        (NLSW, 1988 extract)

        . separate wage ,by(race)

        [output omitted]

    Now suppose the original variable wage is missing in this dataset. It can
    be created using joinvars.

        . drop wage

        . list race wage* in 516/520

             +----------------------------------------+
             |  race      wage1      wage2      wage3 |
             |----------------------------------------|
        516. | white   4.428341          .          . |
        517. | white   15.09662          .          . |
        518. | black          .   6.843801          . |
        519. | other          .          .   6.513685 |
        520. | white   5.072463          .          . |
             +----------------------------------------+

        . joinvars wage = wage1 wage2 wage3

        . list race wage1 wage2 wage3 wage in 516/520

             +---------------------------------------------------+
             |  race      wage1      wage2      wage3       wage |
             |---------------------------------------------------|
        516. | white   4.428341          .          .   4.428341 |
        517. | white   15.09662          .          .   15.09662 |
        518. | black          .   6.843801          .   6.843801 |
        519. | other          .          .   6.513685   6.513685 |
        520. | white   5.072463          .          .   5.072463 |
             +---------------------------------------------------+

    The options

        . joinvars nonsense = wage1 wage2 wage3 ,update missok

        . list race wage1 wage2 wage3 nonsense in 516/520

             +---------------------------------------------------+
             |  race      wage1      wage2      wage3   nonsense |
             |---------------------------------------------------|
        516. | white   4.428341          .          .          . |
        517. | white   15.09662          .          .          . |
        518. | black          .   6.843801          .          . |
        519. | other          .          .   6.513685   6.513685 |
        520. | white   5.072463          .          .          . |
             +---------------------------------------------------+

 
Author

    Daniel Klein, University of Bamberg, klein.daniel.81@gmail.com

Also see

    Online: separate, egen, reshape