The main reason for explicitly constructing the Q matrix is for the pedagogical value of seeing it. As Thomas points out, if you want to actually use Q in a calculation, there will almost always be a much more efficient way of constructing the real goal of the calculation.
For help in that construction, you can use the qr.Q and qr.R functions to see what Q and R look like. This will help you confirm in tiny cases that you have done the more efficient calculation correctly. Rich ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
