princomp and eigen

Have you ever read the help pages? It tells you:

   "Note

   The signs of the columns of the loadings and scores are arbitrary,
   and so may differ between different programs for PCA, and even
   between different builds of R."


Also the references given on ?princomp are really worth reading...

Best,
Uwe Ligges

Hi.
I was comparing the components from  princomp's loadings and the eigen given
the same input.
I found that the sign of componenets (+/-) are opposite between the two
components (from princmop and eigen) but the magnitudes are identical. Why?

Thanks!

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Hi.
I was comparing the components from  princomp's loadings and the eigen given
the same input.
I found that the sign of componenets (+/-) are opposite between the two
components (from princmop and eigen) but the magnitudes are identical. Why?

[Why is the sky blue?  Why are fire engines red?  Why don't they teach
linear algebra these days?]

Because if A%*%x = lambda*x then

A%*%(-x) = lambda*(-x).

     cheers,

         Rolf Turner

P. S.  Why is a duck?  Answer:  Because the higher you go, the
vest has no sleeves.