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help for ddf2dct
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Convert DDF files describing e.g. US Census data to Stata dct and do files

        ddf2dct using filename1 [, dct(filename2) do(filename3) data(filename4)
              drop(varlist) keep(varlist) replace noinfile]

Description

ddf2dct converts Data Definition File (DDF) format files to Stata dct and do
files.  A DDF file contains entries of the form

    -------------------------------------------------------------------------
           D SREFMON     1     25
           T SU: Reference month of this record
                Universe=All persons
           V          1 .First Reference month
           V          2 .Second Reference month
           V          3 .Third Reference month
           V          4 .Fourth Reference month
    -------------------------------------------------------------------------

designed to allow mainframe users to infile data, and is often distributed with
data following standard US Census formats, e.g. the Decennial Census (see also
http://www.nber.org/data/pums.html), the Survey of Income and Program
Participation (SIPP: see also http://www.nber.org/data/sipp.html), and the
Current Population Survey (CPS: see also http://www.nber.org/cps/).

All variable names are converted to lower case.  Variable names in DDF files
are not guaranteed to be legal in Stata, so the following substitutions are
made:

  % becomes p
  - becomes _
  $ becomes d
  
and any variables names that are repeated in the data dictionary have a number
added to the end of their name high enough to make the name distinct from all
previously defined names.  Thus, if a variable FILLER appears four times in the
DDF file, the dct file will have variables filler, filler1, filler2, and
filler3.

Options

dct(filename2) specifies a path and filename where a dictionary file should be
    saved.

do(filename3) specifies a path and filename where a do file that infiles data
    and assigns value labels should be saved.

data(filename4) specifies a path and filename where raw data (to be infiled) is
    saved.

drop(varlist) excludes the variables specified from the dct file.

keep(varlist) includes only the variables specified in the dct file.

replace specifies that the files named may be overwritten if they exist
    already.

noinfile requests no infile command in the created do file.

Examples

    -------------------------------------------------------------------------
        clear
        tempfile do dct s96
        ddf2dct using http://www.nber.org/sipp/1996/sipp96l.ddf, dct(`dct')
            do(`do')
        run `do'
        describe t??amt
        notes t50
        save `s96'
        tempfile do dct s01
        ddf2dct using http://www.nber.org/sipp/2001/sipp01w1.ddf, dct(`dct')
            do(`do')
        clear
        run `do'
        notes t50
        tempfile do dct s93
        ddf2dct using http://www.nber.org/sipp/1993/sipp93w1.ddf, dct(`dct')
            do(`do')
        clear
        run `do'
        notes higrade
        ssc install vlc, replace
        save `s93'
        vlc higrade, to(`s96')
        use `s96', clear
        vlc eeducate, to(`s93')
    -------------------------------------------------------------------------
        clear
        tempfile do dct c89
        ddf2dct using http://www.nber.org/cps/cpsmar89_91.doc, dct(`dct')
            do(`do') drop(FILLER)
        run `do'
        save `c89'
        clear
        tempfile do dct c92
        ddf2dct using http://www.nber.org/cps/cpsmar92.ddf, dct(`dct') do(`do')
            drop(FILLER)
        run `do'
        save `c92'
        ssc install vlc, replace
        vlc a_hga, to(`c89')
        g lab92=trim(substr(label1,1,25)
        ren label2 lab91
        li val lab91 lab92, noo clean
    -------------------------------------------------------------------------

Author

    Austin Nichols
    Urban Institute
    Washington, DC
    austinnichols@gmail.com

Also see

On-line:  help for infiling, label, labelbook, vlc