murdoch@stats.uwo.ca
2005-Nov-18 14:02 UTC
[Rd] pr[in]comp: predict single observation when data has colnames (PR#8325)
On 11/18/2005 7:04 AM, bhx5 at mevik.net wrote:> To my knowledge, this has not been reported previously, and doesn't > seem to have been changed in R-devel or R-patched. > > If M is a matrix with coloumn names, and > > mod <- prcomp(M) # or princomp > > then predicting a single observation (row) with predict() gives the > error > > Error in scale.default(newdata, object$center, object$scale) : > length of 'center' must equal the number of columns of 'x' > > This doesn't happen if M doesn't have coloumn names. > > For instance: > > >>M <- matrix(rnorm(30), ncol = 3) >>mod <- prcomp(M[-1,]) >>predict(mod, newdata = M[1,, drop = FALSE]) > > PC1 PC2 PC3 > [1,] -1.666191 -2.333012 -1.424587 > > >>colnames(M) <- 1:3 >>mod <- prcomp(M[-1,]) >>predict(mod, newdata = M[1,, drop = FALSE]) > > Error in scale.default(newdata, object$center, object$scale) : > length of 'center' must equal the number of columns of 'x' > > > I believe the problem is the line > > newdata <- newdata[, nm] > > in predict.prcomp (line 106 of prcomp.R) and predict.princomp (line 11 > of princomp-add.R), which should probably be > > newdata <- newdata[, nm, drop = FALSE] >Yes, I see the problem, and I agree with your correction. I'll commit a patch. Thanks! Duncan Murdoch