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help for ^_peife^ - 1.6.0 - 2/7/1999
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Utility to decide if estimation sample is used
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    ^_peife^ [^if^ exp] [, ^a^ll]

Description
-----------

^_peife^ modifies the given ^if^ expression to add restrictions to the last
    estimation sample ^e(sample)^. Whem the option ^all^ is specified, the
    ^if^ statement is not modified to add ^e(sample)^.


Output
------

You can retrieve a string with the resulting ^if^ statement by using ^r(if)^.
    For example: local if "`r(if)'"  Note that the resulting string includes
    the work ^if^.

Options
-------

^all^ By default, the ^if^ statement passed to ^_peife^ is modified to add
    ^& e(sample)^. With option ^all^ the ^if^ condition is not changed.
    Consequently, all that is done is the word "if" is placed in front of the
    current ^if^ condition before the string is returned.

Examples within a program
-------------------------
    ...
    * `if' is the curret if condition
    _peife `if',`all'
    * the new condition includes & e(sample)
    local if "`r(if)'"
    * note that `if' has the word if in it
    sum `varlist' `if'
    ...

Note
----

_pesum, _pedum, _pecats do not call _peife. You need to pass the correct if
condition to them.

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Authors: J. Scott Long and Jeremy Freese
         www.indiana.edu/~jslsoc/spost.htm
         spostsup@@indiana.edu