Centring and scaling. The code is very easy to real, and contains x <- as.matrix(x) x <- scale(x, center = center, scale = scale.)
Note that the help page does say The calculation is done by a singular value decomposition of the (centered and scaled) data matrix .... On Mon, 14 Jun 2004, Scott Robbins Loarie wrote: > Thanks very much for showing me these functions, > > In prcomp(), the documentation says that Value: x is "the data > multiplied by the 'rotation' matix". Using sample data: > > data(iris) > iris<-as.matrix(iris[,1:4]) > pcprim<-prcomp(iris, scale=TRUE) > > Why does iris%*%pcprim$rotation (the data multiplied by the rotation > matrix) not equal pcprim$x? > > Thanks very much, > > Scott > > > On Mon, 14 Jun 2004, Prof Brian Ripley wrote: > > > Why are you using the OPRHANED multiv library for a facility covered by > > princomp() and prcomp() in base R? The list might be able to help you > > with the latter, but no one is supporting multiv (hence its status). > > > > On Sun, 13 Jun 2004, Scott Robbins Loarie wrote: > > > > > I am having trouble using the pca function in the multiv library. > > > I am trying to generate the values found in $rproj by using $evecs to > > > calculate linear combinations of my input data. However, I have been not > > > been able to correctly calculate the $rproj values. > > > > > > Using the following standard sample data, why does iris%*%pcprim$evecs[,] > > > not equal pcprim$rproj? > > > > > > data(iris) > > > iris<-as.matrix(iris[,1:4]) > > > pcprim<-pca(iris) > > > > -- > > Brian D. Ripley, [EMAIL PROTECTED] > > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > > University of Oxford, Tel: +44 1865 272861 (self) > > 1 South Parks Road, +44 1865 272866 (PA) > > Oxford OX1 3TG, UK Fax: +44 1865 272595 > > > > -- Brian D. Ripley, [EMAIL PROTECTED] Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272866 (PA) Oxford OX1 3TG, UK Fax: +44 1865 272595 ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html