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 Post subject: HELP ME WIN A BET WITH MY FRIEND (Matlab and LDA)Posted: Fri, 10 Dec 2010 06:03:48 UTC
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Joined: Fri, 10 Dec 2010 05:54:45 UTC
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I have a friend that is putting radar data into MatLab and then uses LDA to obviously reduce the demensionality of the image, however, in the next to last step when matlab produces the "weights" (which might also be considered eigenvalues, I'm not sure) it is giving him complex numbers that he will not be able to put back in matlab to obtain the reduced image. I think he knows how to fix them, we just want to know WHY matlab is giving us complex values.

Thanks!!!

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 Post subject: Re: HELP ME WIN A BET WITH MY FRIEND (Matlab and LDA)Posted: Fri, 10 Dec 2010 06:09:54 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
Posts: 12172
Location: Austin, TX
Aerionne wrote:
I have a friend that is putting radar data into MatLab and then uses LDA to obviously reduce the demensionality of the image, however, in the next to last step when matlab produces the "weights" (which might also be considered eigenvalues, I'm not sure) it is giving him complex numbers that he will not be able to put back in matlab to obtain the reduced image. I think he knows how to fix them, we just want to know WHY matlab is giving us complex values.

Thanks!!!

Ummmm....real matrices can have complex eigenvalues. Just consider

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 Post subject: :-/Posted: Fri, 10 Dec 2010 06:16:02 UTC
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Joined: Fri, 10 Dec 2010 05:54:45 UTC
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Can you explain how? Isn't the only way to be multiplying that matrices by a complex number.

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 Post subject: Re: :-/Posted: Fri, 10 Dec 2010 06:22:40 UTC
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Joined: Wed, 30 Mar 2005 04:25:14 UTC
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Location: Austin, TX
Aerionne wrote:
Can you explain how? Isn't the only way to be multiplying that matrices by a complex number.

What? The eigenvalues are the roots of the characteristic polynomial. This one has characteristic polynomial ...no real roots.

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