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st: about -mreldif( )-


From   "Katsuhide Isa" <katu@ier.hit-u.ac.jp>
To   Statalist <statalist@hsphsun2.harvard.edu>
Subject   st: about -mreldif( )-
Date   Thu, 09 Jun 2005 15:34:14 +0900

Dear Statalisters,

I'm using Stata 8.
I'm dealing with multiple (time series) matrix data(mobility 
tables), and I'd like to compare them to see how they are 
different.

Stata programing manual says that the matrix command 
-mreldif(X, Y)- returns the maximum relative difference between 
two matricies X and Y, and that it is equivalent to 
max(reldif(X, Y)), where reldif(X, Y) returns the "relative" 
difference defined by
                      |X - Y|
                r =  ---------
                      |Y| + 1
calculated element-by-element.

This command may be of use to my study, but I don't understand 
the (mathematical) justification for this formula, and the 
manual seems to provide no further explanation to it.
So, I wonder if there is any good literature (other than Stata 
manuals) as to this formula.

Any suggestions welcome.
Thanks in advance.

K.I.
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