st: egen cut - how to force a category even if zero observations

[Anthony Khawaja <anthonykhawaja@gmail.com>]

Is it possible to force the "egen cut" command to keep a specified category
even though there are zero observations within that category.  For example,
I want to write a script that will work on multiple different datasets, and
I want to categorise age into <40, >=40 <50, >=50 <60, >=60 <70, >=70 <80,
>=80 <90, >=90.  The egen cut command works well unless I have zero
observation in a category - rather than still creating that as a level of
the new categorical variable, Stata just doesn't form the category.  This
would usually be fine, but I am using "file write" commands from which I
want to produce identically shaped tab delimited files to easily overlay
numbers from multiple studies.

I have searched extensively but not found a simple solution.  Of course I
could manually create the new variable, level by level.  But I have many
such variables, and this would be time consuming (and lack elegance!).  Does
anyone know of an elegant solution?

For example, in one dataset, there are no participants <40 years.  So the
following command yields one less level in the categorical variable produced
than I wanted:

. egen agecut = cut(age), at (0 40 50 60 70 80 90 130) label


. tab agecut

     agecut |      Freq.     Percent        Cum.
------------+-----------------------------------
        40- |         29        0.39        0.39
        50- |        873       11.73       12.12
        60- |      3,540       47.56       59.67
        70- |      2,364       31.76       91.43
        80- |        629        8.45       99.88
        90- |          9        0.12      100.00
------------+-----------------------------------
      Total |      7,444      100.00


Many thanks in advance for any advice.

Anthony



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