```Date: Tue, 23 Apr 1996 21:16:02 +0100 Reply-To: Jose Luis Alabart Sender: "SAS(r) Discussion" From: Jose Luis Alabart Subject: Re: Geometric Row Mean What about this code? DATA D1; INPUT X1 X2 X3 X4; gmean=exp(mean(log(x1),log(x2),log(x3),log(x4))); CARDS; 1 1 1 1 2 2 2 2 1 2 1 2 3 4 5 6 1 10 100 1000 ; PROC PRINT; RUN; The SAS System 1 20:46 Tuesday, April 23, 1996 OBS X1 X2 X3 X4 GMEAN 1 1 1 1 1 1.0000 2 2 2 2 2 2.0000 3 1 2 1 2 1.4142 4 3 4 5 6 4.3559 5 1 10 100 1000 31.6228 Perhaps it is a little tedious, but it works... nad there is nothing that can't be solved by "copy-paste" and "replace"... :-) >I posted a question last week about computing the row geometric mean of a >series of 30 or 40 adjacent variables. Several kind souls came up with >what seemed to be fairly easy solutions to the problem, except when I >tried them they didn't work correctly. > >One solution was: > >gmean = exp(mean(log(x1 -- x40))); > >This solution takes advantage of the fact that the arithmetic mean of >logarithms is equal to the logarithm of the geometric mean, which can in >turn be reconstituted to its original form via the exp function. >This solution is imminently logical and causes no problem, except that it >gives the wrong answer. When tested with a small number of variables, it >appears to take the logarithm of the sum of x1+x2+x3+x4 (in a four >variable case), instead of summing the logs of x1, x2, x3, x4. I'm using >SAS 6.11. > >Any other ideas, or comments on what is actually wrong with the code above. > >Thank you very much for your time. > > *********************************************************************** > * Dr. Marc R. Feldesman | email: feldesmanm@pdx.edu| Beyond every * > * Professor and Chairman | fax: (503)-725-3905 | credibility * > * Anthropology Department | voice: (503)-725-3081 | gap lies a * > * Portland State University | pager: (503)-870-2515 | gullibility * > * Portland, Oregon 97207 | home: NOT | fill * > *********************************************************************** J.L. Alabart Servicio de Investigacion Agraria Apdo. 727 50080 Zaragoza (Spain) FAX: (Spain) 76 57 55 01 Voice: (Spain) 76 57 63 36 (Spain) 76 57 63 11 Tx. 58194 IDAE E E-mails: JOSELUIS@mizar.csic.es (or) ALABART@cc.unizar.es ```

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