bates at stat.wisc.edu
Fri Jan 17 14:46:03 CET 2003
"kjetil brinchmann halvorsen" <kjetil at entelnet.bo> writes:
> On 16 Jan 2003 at 22:15, Yan Yu wrote:
> > HI,
> > i have some prob when i try to use nls().
> > my data is 1D vector, I tried to use a polynomial function(order is 3) to
> > fit it.
> > the data series is stored in x.
> > the a0, a1, a2, a3 below is coefficient, which i hope i can get from
> > calls "nls"
> > > z <- nls( ~ a0 + a1 * x + a2 * x * x + a3 * x * x * x, data = x )
> You haven't given a response in the formula? nls could possibly give
> a more informative error message.
and you didn't give starting estimates for the parameters and the
model should not be fit with nls in the first place. A polynomial in
x is a linear model in the coefficients a0, a1, a2, and a3 and should
be fit with lm, not nls.
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