: [R] poly regression
They have different coefficients because their model matrices are different
but they both lead to the same predictions:
> fitted(lm(y~1+x+I(x^2)))
1 2 3 4 5 6 7 8 9 10
1 4 9 16 25 36 49 64 81 100
> fitted(lm(y~poly(x,2)))
1 2 3 4
They have different coefficients because their model matrices
are different but they both lead to the same predictions:
> fitted(lm(y~1+x+I(x^2)))
1 2 3 4 5 6 7 8 9 10
1 4 9 16 25 36 49 64 81 100
> fitted(lm(y~poly(x,2)))
1 2 3 4 5 6 7 8 9 10
1
hi,
I want to do a polynomial regression of y on x of degree 2, as following
> x<-1:10
> y<-x^2
> lm(y~poly(x,2))
Call:
lm(formula = y ~ poly(x, 2))
Coefficients:
(Intercept) poly(x, 2)1 poly(x, 2)2
38.5099.9122.98
Which is not what i had expected.
If I wrote the expre
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