The documentation for lm() indicates that the 'qr' component of an
lm object is optional. But some functions do not behave well when
this component is absent: summary() gives an error and predict()
returns all zeroes.
Example:
> x <- 1:10; y <- x^2
> mm <- lm(y~x, qr=FALSE)
> summary(mm)
Error in summary.lm(mm) : invalid 'lm' object: no 'terms'
nor 'qr'
component
> predict(mm, newdata=data.frame(x=11:15))
1 2 3 4 5
0 0 0 0 0
> predict(mm, newdata=data.frame(x=11:15), se=TRUE)
Error in qr.R(object$qr) : argument is not a QR decomposition
> R.version
_
platform i386-pc-mingw32
arch i386
os mingw32
system i386, mingw32
status
major 2
minor 3.0
year 2006
month 04
day 24
svn rev 37909
language R
version.string Version 2.3.0 (2006-04-24)
J. R. M. Hosking