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From: Jamie on 5 Aug 2010 08:50
I am having trouble finding out how matlab derives the coefficients (coefs) using the princomp function. I am using a 46x800 matrix of count rate (counts per second) data (46 variables). I am using the first two columns of the coefs (each containing 46 values) which I believe relate to the 1st and 2nd principal component. I would appreciate any advice on what these two columns are and how they are derived. I am trying to calculate the error/ uncertainty of these first two columns, but without understanding how matlab has obtained/ derived these from the raw data, I am finding it extremely difficult. I know the errors associated with each of the 46x800 count rates from my raw data, so any advice would be appreciated. Regards
From: Steven_Lord on 5 Aug 2010 09:18


"Jamie " <j.adams3(a)lancaster.ac.uk> wrote in message
news:i3ec2d$akt$1(a)fred.mathworks.com...
> I am having trouble finding out how matlab derives the coefficients
> (coefs) using the princomp function. I am using a 46x800 matrix of count
> rate (counts per second) data (46 variables). I am using the first two
> columns of the coefs (each containing 46 values) which I believe relate to
> the 1st and 2nd principal component. I would appreciate any advice on what
> these two columns are and how they are derived. I am trying to calculate
> the error/ uncertainty of these first two columns, but without
> understanding how matlab has obtained/ derived these from the raw data, I
> am finding it extremely difficult. I know the errors associated with each
> of the 46x800 count rates from my raw data, so any advice would be
> appreciated. Regards

Have you reviewed the four references given on the function reference page,
as well as the documentation page discussing principal component analysis
that is listed in the See Also section of that page?

http://www.mathworks.com/access/helpdesk/help/toolbox/stats/princomp.html

--
Steve Lord
slord(a)mathworks.com
comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

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