On Tue, 2006-10-17 at 12:34 -0700, Li Zhang wrote:
> Y X Z
> 42.0 7.0 33.0
> 33.0 4.0 41.0
> 75.0 16.0 7.0
> 28.0 3.0 49.0
> 91.0 21.0 5.0
> 55.0 8.0 31.0
>
>
> data<-read.table("d.txt",header=TRUE)
> mod<-lm(data$Y~data$X+data$Z)
> ---------------------------------------
>
> I would like to know the predict value at a new level,
> say
>
> X=10 Z=30
> dat <- scan()
1: 42.0 7.0 33.0
4: 33.0 4.0 41.0
7: 75.0 16.0 7.0
10: 28.0 3.0 49.0
13: 91.0 21.0 5.0
16: 55.0 8.0 31.0
19:
Read 18 items
> dat <- as.data.frame(matrix(dat, ncol = 3, byrow = TRUE))
> names(dat) <- c("X","Y","Z")
> dat
X Y Z
1 42 7 33
2 33 4 41
3 75 16 7
4 28 3 49
5 91 21 5
6 55 8 31
> mod <- lm(Y ~ X + Z, data = dat) # note use of data argument
> pred <- predict(mod, newdata = list(X = 10, Z = 30))
> pred
[1] -0.003469617
or
> pred <- predict(mod, newdata = data.frame(X = 10, Z = 30))
> pred
[1] -0.003469617
HTH
G
>
> Is there a function available to calculate it
> directly?
>
> Thank you
>
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Gavin Simpson [t] +44 (0)20 7679 0522
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