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Tabulate string variables split into parts

        tabsplit strvar [if exp] [in range] [ , characters
                 parse(parse_strings) [no]trim tabulate_options ]


Description

    tabsplit tabulates frequencies of occurrence of the parts of a string
    variable. By default, the parts of a string are separated by spaces. The
    parts of "A B C" are thus "A", "B" and "C". Optionally, alternative
    parsing strings may be specified. The parts of "A,B,C" with parse(,) are,
    again, "A", "B" and "C". The parts of "A B C" with parse(,) are just the
    single part "A B C".  The idea of a part thus generalises Stata's concept
    of a word.


Remarks 

    Suppose data are gathered on modes of transport used in the journey to
    work. In addition to values of "car", "cycle", "foot", and so forth,
    there may be multiple values such as "car train tube foot" for people who
    use two or more modes. Within the limits in your version of Stata such
    single or multiple values may be stored as string variables.  It may then
    be desired, for example, to count the individual modes used.  tabsplit is
    designed for this special problem.

    By default, leading and trailing spaces are ignored. Thus, string values
    that equal one or more spaces are treated just as if they were missing.
    Also with " 1,  2,   3" and parse(,) the parts are "1", "2" and "3".


Options

    characters specifies that strings are to be split into separate
        characters. Thus strings such as "ABCDE" and "ABC" will be split so
        that the frequencies of "A", "B", etc. will be tabulated.  parse() is
        ignored if characters is specified.

    parse(parse_strings) specifies that, instead of spaces, parsing should be
        done using one or more parse_strings. Most commonly, one string which
        is a single punctuation character will be specified.  For example, if
        parse(,) is specified, then "1,2,3" is split into "1", "2" and "3".

        It is also possible to specify (1) two or more strings which are
        alternative separators of parts and/or (2) strings which consist of
        two or more characters.  Alternative strings should be separated by
        spaces and strings which include spaces should be bound by " ". Thus
        if parse(, " ") is specified, then "1,2 3" is also split into "1",
        "2" and "3".  Note particularly the difference between (say)
        parse(a b) and parse(ab): with the first, "a" and "b" are both
        acceptable as separators, while with the second, only the string "ab"
        is acceptable.

    notrim specifies that the original string variable should not be trimmed
        of leading and trailing spaces before being parsed, and that the
        parts should not be trimmed similarly before being tabulated. notrim
        is not considered compatible with parsing on spaces, as the latter
        implies that spaces in a string are to be discarded: either specify
        parse strings or by default allow a trim.

    tabulate_options are options of tabulate with one variable. The most
        useful in practice is sort. Note that the table is based on a
        temporary dataset which does not remain in memory after tabsplit has
        finished.


Examples

    . tabsplit authors, parse(,) sort


Author 

    Nicholas J. Cox, University of Durham, U.K.
    n.j.cox@durham.ac.uk


Also see

    On-line:  help for split, tabulate