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Re: Principal Components


Covariance is the default method


$Version


"9.0 for Mac OS X x86 (64-bit) (January 24, 2013)"


Options[PrincipalComponents]


{Method -> "Covariance"}


mat = {{1., 2}, {2, 3}, {4, 10}};


pc1 = PrincipalComponents[mat]


{{3.27053, 0.285293}, {1.99969, -0.335165}, {-5.27023, 0.0498715}}


pc1 == PrincipalComponents[mat,
  Method -> "Covariance"] ==
 PrincipalComponents[pc1] ==
 PrincipalComponents[pc1,
  Method -> "Covariance"]


True


pc2 = PrincipalComponents[mat,
  Method -> "Correlation"]


{{1.10388, 0.130549}, {0.478746, -0.170139}, {-1.58262, 0.0395904}}


pc2 == PrincipalComponents[pc2] ==
 PrincipalComponents[pc2,
  Method -> "Covariance"]


True



Bob Hanlon




On Tue, Oct 22, 2013 at 12:49 AM, pw <p.willis at telus.net> wrote:

>
> Hello,
>
> The function 'PrincipalComponents' returns the the first principal
> components vector of a group of input vectors.
>
> Question 1.) Is it possible to define Method->"covariance" or is
> correlation the only PC technique available?
>
> Question 2.) How can I generate an inverse PC transform from my
> PrincipalComponents output?
>
>
> Thanks,
>
>
> Peter
>
>




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