Hello octaveforge developers,
I am reporting again about the xcorr(...,'coeff') matlab compatibility issue
(or bug ?!):
see previous message for description.
This problem can be easily solved by changing current lines 174 to 175 in
xcorr.m
elseif strcmp(scale,'coeff')
R = R ./ ( ones(rows(R),1) * R(maxlag+1, :) );
to:
elseif strcmp(scale,'coeff')
if isempty(Y)
sumx2=sum(abs(X).^2);
csumx2=sumx2.'*sumx2;
R = R ./ sqrt( ones(rows(R),1) * csumx2(:).' );
else
R = R / sqrt( sum(abs(X).^2) * sum(abs(Y.^2)) );
end
Regards
Nitzan Arazi
From: [email protected]
To: [email protected]
Subject: xcorr incompatibilty
Date: Mon, 4 Feb 2008 09:04:58 +0200
Hello octaveforge developers,
I have found some incompatibility of the xcorr function between Octave and
Matlab.
When using c=xcorr(x,y,'coeff'), the 'coeff' scale is used by Octave to
normalize the cross correlation c at lag=0 to the value 1.0.
On the other hand, Matlab uses the 'coeff' scale to normalize the the cross
correlation with an equivalent factor such that the autocorrelations of both x
and y are 1.0 at lag=0 !
This produce different scaling by xcorr(x,y,'coeff') in Octave and Matlab !
I assume that this is not a bug since the different behavior is clearly
documented as different. It may be useful to change the definition of Octave's
xcorr scale parameter to be compatible with Matlab definition (this can be
easily done in the xcorr.m code).
Nitzan Arazi
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