R: How to create a function from a model?

Question

I am using an automatic model selection procedure, "step". The model of depart (the biggest possible) is a polynom, say of the 4th degree.

Depart<-lm(y~x+I(x^2)+I(x^3)+I(x^4))

Final<-step(Depart)

I need to transform the Final model to a corresponding function. How can i do this?

NPE · Accepted Answer · 2010-11-18 12:00:38Z

8

Do you mean something like this:

f<-function(newdata)predict(Final,data.frame(x=newdata))

?

answered Nov 18, 2010 at 12:00

NPE

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$\begingroup$ No, i wish to construct a function of one variable. Something like "ff<-function(x) 3.23+2.78x-3.45x^4". $\endgroup$
– Roah
Commented Nov 18, 2010 at 12:49
2

$\begingroup$ @Roah Did you try the answer? Because that's exactly what it will give you (you won't see the coefficients, but why do you care about the internals of the function? $\endgroup$
– Aniko
Commented Nov 18, 2010 at 13:54
$\begingroup$ @Roah - Could you explain in what way the function I suggested does not do what you expect? It certainly accepts scalars so you can call it with a single value. Is the return value not what you are expecting? $\endgroup$
– NPE
Commented Nov 18, 2010 at 13:55
$\begingroup$ Sorry, aix! I was too bothered by the internal structure of the algorithm... And it is very simple! Thanks a lot, because i was going to parse the output... $\endgroup$
– Roah
Commented Nov 18, 2010 at 15:04

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