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

René Mayer mayer at psychologie.tu-dresden.de
Fri Sep 9 11:01:33 CEST 2011


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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