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help for ^rprod^                                                   (STB-60: dm87)
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Calculating the row product of observations
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  ^egen^ newvar ^=^ ^rprod(^varlist^)^ [^if^ exp] [^in^ range]
                     [^, pm^iss^(ignore^|^missing^|^1)^]


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

^rprod^ provides a multiplicative row function for ^egen^ analogous to the
additive ^rsum^ function.  The product of observations of varlist
meeting optional ^in^ and ^if^ conditions is returned in newvar. ^rprod^
insists that newvar is calculated in double precision.


Option
------

^pmiss(ignore^|^missing^|^1)^ specifies what is to be the product of 
    observations at least one of which is missing.  This syntax maintains 
    consistency with that of another ^egen^ function, ^prod^.

   ^pmiss(ignore)^, the default, ignores missing values and returns the
        product of all non-missing values. If all values are missing, then
        missing is returned.

   ^pmiss(missing)^ returns missing for the product of observations if
        any observation is missing.  This holds even if one or more of the
        nonmissing observations is zero.

   ^pmiss(1)^ returns 1 for the product of observations if all observations
        are missing. Otherwise, it returns the product of all nonmissing 
        values. This choice would rarely be made (see Appendix in STB-51 
        insert for dm71: ^_gprod^; STB Reprints Vol 9, pages 45--48).


Examples
--------

    . ^egen k = rprod(a b c)^

    . ^egen m = rprod(a b c), pmiss(missing)^


Acknowledgements
----------------

This program was written in response to a thread on the Statalist Server
started by Brian Jacob (ba-jacob@@mail.consortium-chicago.org ). Nick Cox
(n.j.cox@@durham.ac.uk) provided helpful comments.


Author
------

      Philip Ryan
      Department of Public Health
      University of Adelaide
      South Australia
      philip.ryan@@adelaide.edu.au


Also see
--------

    Manual:  [R] ^egen^
       STB:  STB-51 dm71 
   On-line:  help for ^egen^, ^prod^