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
38.50 99.91 22.98
Which is not what i had expected.
If I wrote the expression in an explicit form, y~1+x+I(x^2), I could
get the expected result:
> lm(y~1+x+I(x^2))
Call:
lm(formula = y ~ 1 + x + I(x^2))
Coefficients:
(Intercept) x I(x^2)
0 0 1
What is the diff between them?
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