[R] Problem with predict.lm()

[Martin Spindler]

Dear all,
 
the following example somehow uses the "old data" (X) to make the predictions, but not the new data Xnew as intended.
 
y <- rnorm(100)
X <- matrix(rnorm(100*10), ncol=10)
lm <- lm(y~X)
Xnew <- matrix(rnorm(100*20), ncol=10)
ynew <- predict(lm, newdata=as.data.frame(Xnew)) #prediction in not made for Xnew
 
How can I foce predict.lm to use use the new data?
 
Thank you very much for your efforts in advance!
 
Best,
 
Martin