[R] prcomp: results with reversed sign in output?

[Paul Hiemstra]

 Hi,

If all the signs are switched the PC's are still the same. The principal
vectors are along the same axis, only in a different direction. So there
is no problem :).

hope this helps,
Paul

On 09/09/2011 09:01 AM, René Mayer wrote:
> Dear All,
>
> when I'm running a PCA with
>
> prcomp(USArrests, scale = TRUE)
>
> I get the right principal components, but with the wrong sign infront
>
> Rotation:
> PC1 PC2 PC3 PC4
> Murder 0.5358995 -0.4181809 0.3412327 0.64922780
> Assault 0.5831836 -0.1879856 0.2681484 -0.74340748
> UrbanPop 0.2781909 0.8728062 0.3780158 0.13387773
> Rape 0.5434321 0.1673186 -0.8177779 0.08902432
>
> instead of
>
> PC1 PC2 PC3 PC4
> Murder -0.5358995 0.4181809 -0.3412327 0.64922780
> Assault -0.5831836 0.1879856 -0.2681484 -0.74340748
> UrbanPop -0.2781909 -0.8728062 -0.3780158 0.13387773
> Rape -0.5434321 -0.1673186 0.8177779 0.08902432
>
> what is happening here?
> any ideas?
>
> thanks,
> René
>
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-- 
Paul Hiemstra, Ph.D.
Global Climate Division
Royal Netherlands Meteorological Institute (KNMI)
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