[E] Y = a + b*sin(d*x+phi)
isn't a linear model and therefore can't be estimated with lm() --
you will need
some heavier artillery. Linear as in lm() means "linear in parameters."
(As it happens, I'm adapting Gordon Smyth's pronyfreq S code for the
above
problem this afternoon, and have been wondering why someone else hasn't
already done this? Any clues?
url: www.econ.uiuc.edu/~roger Roger Koenker
email rkoen...@uiuc.edu Department of Economics
vox: 217-333-4558 University of Illinois
fax: 217-244-6678 Champaign, IL 61820
On Jan 12, 2009, at 4:57 PM, Carl Witthoft wrote:
Well..... *_* ,
I think it should have been clear that this was not a question for
which any code exists. In fact, I gave two very specific examples
of function calls. The entire point of my question was not "what's
up with my (putative) code and data " but rather to try to
understand the overarching philosophy of the way lm() treats the
function it's given.
I do understand the sneaky ways to make it do a linear fit with or
without forcing the origin. And, sure, I could have run a data set
thru a bunch of different quadratic-like functions to try to see
what happens.
Let me pick a more complicated example. The general case of a sin
fit might be Y = a + b*sin(d*x+phi) .(where, to be pedantic, x is
the only data input. All others are coefficients to be found)
If I try y<-lm(yin~I(sin(x))), what is the actual fit function?
And so on.
That's why I was hoping for a more general explanation of what lm()
does.
Charles C. Berry wrote:
On Mon, 12 Jan 2009, c...@witthoft.com wrote:
[nothing deleted]
matplot(1:100, lm(rnorm(100)~poly(1:100,4),x=T)$x ) # for example
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......^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Charles C. Berry (858) 534-2098
Dept of Family/
Preventive Medicine
E mailto:cbe...@tajo.ucsd.edu UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/ La Jolla, San Diego
92093-0901
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