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Title

    [D] mvencode -- Change missing values to numeric values and vice versa


Syntax

    Change missing values to numeric values

        mvencode varlist [if] [in], mv(#|mvc=# [\ mvc=#...] [\ else=#])
                  [override]


    Change numeric values to missing values

        mvdecode varlist [if] [in], mv(numlist | numlist=mvc
                  [\ numlist=mvc...])


    where mvc is one of .|.a|.b|...|.z


Menu

    mvencode

        Data > Create or change data > Other variable-transformation commands
            > Change missing values to numeric

    mvdecode

        Data > Create or change data > Other variable-transformation commands
            > Change numeric values to missing


Description

    mvencode changes missing values in the specified varlist to numeric
    values.

    mvdecode changes occurrences of a numlist in the specified varlist to a
    missing-value code.

    Missing-value codes may be sysmiss (.) and the extended missing-value
    codes .a, .b, ..., .z.

    String variables in varlist are ignored.


Options

        +------+
    ----+ Main +-------------------------------------------------------------

    mv(#|mvc=# [\ mvc=#...] [\ else=#]) is required and specifies the numeric
        values to which the missing values are to be changed.

        mv(#) specifies that all types of missing values be changed to #.

        mv(mvc=#) specifies that occurrences of missing-value code mvc be
        changed to #.  Multiple transformation rules may be specified,
        separated by a backward slash (\).  The list may be terminated by the
        special rule else=#, specifying that all types of missing values not
        yet transformed be set to #.

        Examples: mv(9), mv(.=99\.a=98\.b=97), mv(.=99\else=98)

    mv(numlist | numlist=mvc [\ numlist=mvc...]) is required and specifies
        the numeric values that are to be changed to missing values.

        mv(numlist=mvc) specifies that the values in numlist be changed into
        missing-value code mvc.  Multiple transformation rules may be
        specified, separated by a backward slash (\).  See [[U]] 11.1.8
        numlist for the syntax of a numlist.

        Examples: mv(9), mv(99=.\98=.a\97=.b), mv(99=.\100/999=.a)

    override specifies the protection provided by mvencode be overridden.
        Without this option, mvencode refuses to make the requested change if
        any of the numeric values are already used in the data.


Examples

    ---------------------------------------------------------------------------
    Setup
        . sysuse auto

    Translate missing values in the data to 999
        . mvencode _all, mv(999)

    Change 999 values back to missing values
        . mvdecode _all, mv(999)

    List the data
        . list rep78 if rep78 == .

    Set rep78 to 999 in observation 3
        . replace rep78 = 999 in 3

    Try to translate missing values in the data to 999
        . mvencode _all, mv(999)

    Force the translation of missing values in the data to 999
        . mvencode _all, mv(999) override

    ---------------------------------------------------------------------------
    Setup
        . sysuse auto, clear

    List the data
        . list rep78 foreign if rep78 == .

    Translate missing values for rep78 to 998 if foreign is Domestic and
    translate to 999 if foreign is Foreign
        . mvencode rep78 if foreign == 0, mv(998)
        . mvencode rep78 if foreign == 1, mv(999)

    List the data
        . list rep78 foreign if rep78 > 900

    For rep78, translate 998 to . and 999 to .a
        . mvdecode rep78, mv(998=. \ 999=.a)

    List the data
        . list rep78 foreign if rep78 >= .
    ---------------------------------------------------------------------------


Also see

    Manual:  [D] mvencode

      Help:  [D] generate, [D] recode

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