On Mon, Feb 28, 2011 at 08:41:02AM -0800, knut-o wrote:
> Hi
> I have a x-list and a y-list and I'm trying to make a line that goes ca.
> through the dots. I want to find a, b and c in ax^2 + bx + c.
> How to do?
Hi.
Try the following
x <- rnorm(100)
y <- 4*x^2 + 3*x + 2 + 0.2*rnorm(100)
z <- poly(x, degree=2, raw=TRUE)
lm(y ~ z)$coefficients
(Intercept) z1 z2
2.000131 3.013591 4.000884
or also
x2 <- x^2
lm(y ~ x + x2)$coefficients
with the same result.
Hope this helps.
Petr Savicky.
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