simple predict question

Alternatively, one can convert dat to a data frame first (?lm states that data is "an optional data frame containing the variables in the model."):

dat<-matrix(c(0,0,10,20),2,byrow=T)
dat <- as.data.frame(dat)
lm1<-lm(V2~V1, dat)
predict(lm1, data.frame(V1=seq(0,10,1)))
 1  2  3  4  5  6  7  8  9 10 11 
 0  2  4  6  8 10 12 14 16 18 20 

Cheers .........

Peter Alspach

Gabor Grothendieck <ggrothendieck at gmail.com> 01/06/05 09:00:15 >>>

Excuse the simple question...
I'm not sure what I'm doing wrong with predict, but let me use this example:
Suppose I do:
dat<-matrix(c(0,0,10,20),2,byrow=T)
lm1<-lm(dat[,2]~dat[,1])

Suppose I want to generate the linearly-interpolated y-values between the
point (0,0) and (0,20) at every unit interval.
I thought I just do:
predict(lm1, data.frame(seq(0,10,1))) to get 0,2,4,6...,18,20, but instead
I just get:
1    2
0  20

I think the names are confusing it.  Try:

x <- dat[,1]; y <- dat[,2]
lm1 <- lm(y ~ x)
predict(lm1, data.frame(x = 1:10))

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