From bug-request at octave dot org Thu Dec  2 08:26:22 2004
Subject: bug beetwen sum and mean
From: Etienne de Foras <e_deforas at yahoo dot fr>
To: bug-octave at octave dot org
Date: Thu, 2 Dec 2004 06:31:22 -0600

Hello,

First, thanks for this very nice software!!!

This bug concerne the calculus of mean along a dimension, it may be not consitent with sum:
the result given on a vector line, by mean(...,1) does not have the same dimension with sum(...,1)

just trying this:

d=rand(1,5); mean(d,1)
gives:

dim=1 ans= 0.522 (or an other value)

and
sum(d,1)
gives
ans= 0.23 0.56 0.14 0.7 0.6 

Normally sum and mean shall return vectors with the same dimensions.
I think that sum is OK since I explicitely wanted the sum along dimension 1, there is one row so
its return the same vector.
For mean, its force the calculus along dimension 2, this is not what I asked ( for this I would
just  give no dimension or 2) , it shall return the same vector (like sum).

I am using this function to avoid this bug (and other for center, std, studentize...):

function mn=vector_mean(a)
	if rows(a)<2
#		disp('using simplified mean')
		mn=a;
		return;	
	endif;
	mn=mean(a);
endfunction

But of course, it would be preferable to modify mean.m itself .

By the way  center, std, and studentize may be concerned too . 

Thanks and see you...

PS : version= 2.1.50 on win32


	

	
		
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