help marktouse, help svymarktouse
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Title

    marktouse -- Mark observations to be used


Syntax

        marktouse markvar [varlist] [if] [in] [weight] [, label(label)
               zeroweight ]

        svymarktouse markvar [varlist] [if] [in] [, label(label) ]


    aweights, fweights, pweights, and iweights are allowed with marktouse;
    see weight.
    Time-series operators are allowed; see tsvarlist.


Description

    marktouse creates a 0/1 marker variable recording which observations are
    to be used in subsequent commands. The marker variable is set to 1 in
    observations for which none of the specified variables contain missing,
    that satisfy the if and in qualifiers, and have a strictly positive,
    non-missing weight and is set to 0 in all other observations. Note that
    marktouse is intended for use in interactive mode or in do-files. Do not
    use marktouse within Stata programs. Use official marksample in Stata
    programs.

    Working with a marker variable is useful if you want to ensure that all
    commands use the same observations. See "Stata tip 44: Get a handle on
    your sample" in the Stata Journal (in press). The procedure is to type

        . marktouse markvar ...
        
    at the beginning of an analysis and include if markvar in all subsequent
    commands, as in

        . regress ... if markvar

    svymarktouse is like marktouse but, additionally, sets the marker
    variable to 0 wherever any of the survey-characteristic variables
    (previously set by svyset) contain missing. Essentially, svymarktouse is
    marktouse followed by svymarkout.

    Warning: Do not use the if and in qualifiers in svymarktouse to restrict
    analyses to subpopulations. To compute estimates for subpopulations in
    complex survey data, use svy's subpop() option.


Options

    label(label) attaches a label (up to 80 characters) to the marker
        variable.

    zeroweight indicates that zero weights are not to be excluded.


Examples

        . sysuse auto
        (1978 Automobile Data)
        
        . marktouse touse price weight rep78
        (69 observations marked)
        
        . quietly regress price weight if touse
        
        . estimates store model1
        
        . quietly xi: regress price weight i.rep78 if touse
        
        . estimates store model2
        
        . estimates table model1 model2, stats(N)
        
        ----------------------------------------
            Variable |   model1       model2    
        -------------+--------------------------
              weight |  2.0124198     2.440292  
           _Irep78_2 |               783.90092  
           _Irep78_3 |               1379.1152  
           _Irep78_4 |               2068.2672  
           _Irep78_5 |               3245.2724  
               _cons |    44.3284   -3000.4051  
        -------------+--------------------------
                   N |         69           69  
        ----------------------------------------
        

Returned results

    r(N)       scalar containing the number of marked observations
    r(markvar) macro containing the name of marker variable


References

    Jann, B. (in press). Stata tip 44: Get a handle on your sample. The Stata
        Journal 7(2).


Author

    Ben Jann, ETH Zurich, jann@soz.gess.ethz.ch


Also see