Same eigenvalues but different eigenvectors using 'prcomp' and 'principal' commands

Arlindo Meque <mequitomz <at> yahoo.com.br> writes:

Dear all,

I've used the 'prcomp' command to
calculate the eigenvalues and eigenvectors of a  matrix(gg).

Using the command 'principal' from the
'psych' package?  I've performed the same exercise. I  got the same
eigenvalues but different eigenvectors. Is there any reason for that
difference?

[snip]


  eigenvectors are only defined up to a scale factor.  prcomp is
scaling them so that the sum of squares is 1; I haven't bothered
to see how principal() is scaling them (maybe the documention says).

(1,1) and (-1,1)   , or (1,1) and (1,-1), would have been
equally valid choices.

  Ben Bolker