hi, my linear model is y=c+a*x1+b*x2 i tried to found a, c, b by the use of: mymodel<-lm(y~1+x1+x2) where y, x1, x2 are 3 vectors with the same length the result is a=NA.so i want to know where is the problem. -- View this message in context: http://www.nabble.com/lm%28%29-function-tp17546079p17546079.html Sent from the R help mailing list archive at Nabble.com.