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help for ^rprod^                                                    
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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)^]
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Description
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^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.
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Option
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^pm^iss^(ignore|missing|1)^ specifies what is to be the product of a group
    at least one of whose observations is missing.  This is to maintain 
    consistency with another ^egen^ function, ^prod^.
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   ^pm^iss^(ignore)^, the default, ignores missing values and returns the
        product of all non-missing values in the group. If all values are
        missing, then missing is returned.
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   ^pm^iss^(missing)^ returns missing for the product of observations in
        a group if any observation in the group is missing.
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   ^pm^iss^(1)^ returns 1 for the product of observations in a group
        if all observations in the group are missing. Otherwise it
        returns the product of all non-missing values. This choice would
        rarely be made (see Appendix in STB-51 insert for ^_gprod^).
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Examples
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^. list a b c^

             a          b          c 
  1.         1          1          1  
  2.         2          3          4  
  3.         0          1          5  
  4.         5          0          1  
  5.         0          0          0  
  6.         .          .          .  
  7.         1          .          1  
  8.         8          3          .  
  9.         0          .          0  
 10.         .          0          .  
 11.         .          .          0  
 12.         .          .          6  
 13.        -3          4          5  
 14.        -1         -7          2  
 15.         .          .         -4

^. egen k = rprod(a b c )^
(1 missing value generated)

^. list^

             a          b          c           k 
  1.         1          1          1           1  
  2.         2          3          4          24  
  3.         0          1          5           0  
  4.         5          0          1           0  
  5.         0          0          0           0  
  6.         .          .          .           .  
  7.         1          .          1           1  
  8.         8          3          .          24  
  9.         0          .          0           0  
 10.         .          0          .           0  
 11.         .          .          0           0  
 12.         .          .          6           6  
 13.        -3          4          5         -60  
 14.        -1         -7          2          14  
 15.         .          .         -4          -4  

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

^. list^

             a          b          c           k           m 
  1.         1          1          1           1           1  
  2.         2          3          4          24          24  
  3.         0          1          5           0           0  
  4.         5          0          1           0           0  
  5.         0          0          0           0           0  
  6.         .          .          .           .           .  
  7.         1          .          1           1           .  
  8.         8          3          .          24           .  
  9.         0          .          0           0           .  
 10.         .          0          .           0           .  
 11.         .          .          0           0           .  
 12.         .          .          6           6           .  
 13.        -3          4          5         -60         -60  
 14.        -1         -7          2          14          14  
 15.         .          .         -4          -4           .  


Author
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      Philip Ryan
      Department of Public Health
      University of Adelaide
      South Australia
      philip.ryan@@adelaide.edu.au
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Also see
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 Manual:  [R] ^egen^
  STB-51:  ^_gprod^
On-line:  help for ^egen^ ^prod^