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Student Support Forum: 'Principal Components' topicStudent Support Forum > General > Archives > "Principal Components"

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Adam
07/12/13 06:13am

Im having issues with the following,

I notice while computing the Principal Components of a data set using Mathematica 8.0 the magnitude of the outputs are correct there seems to be an issue with their signs.

Finding the online help file

PrincipalComponents[{{1, 2}, {2, 3}, {4, 10}}]

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

http://reference.wolfram.com/mathematica/MultivariateStatistics/ref/PrincipalComponents.html

When computed in my notebook I find

Needs["MultivariateStatistics`"]
N[PrincipalComponents[{{1, 2}, {2, 3}, {4, 10}}]]

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

Obviously the difference here is * -1 but i'm encountering this issue on much larger data sets where the solution is not simply solved by * -1.

Can anyone advice in what is going wrong during my notebook computation

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