Michael wrote: >> pca=prcomp(training_data, center=TRUE, scale=FALSE, retx=TRUE); > > Then I want to rotate the test data set using the > >> d1=scale(test_data, center=TRUE, scale=FALSE) %*% pca$rotation; >> d2=predict(pca, test_data, center=TRUE, scale=FALSE); > > these two values are different > >> min(d2-d1) > [1] -1.976152 >> max(d2-d1) > [1] 1.535222
This is because you have subtracted a different means vector. You should use the coloumn means of the training data (as predict does; see the last line of stats:::predict.prcomp): d1=scale(test_data, center=pca$center, scale=FALSE) %*% pca$rotation; -- Bjørn-Helge Mevik ______________________________________________ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
