On 10/18/2009 11:26 PM, tdm wrote:
> I have build a model but want to then manipulate the coefficients in some
> way.
>
> I can extract the coefficients and do the changes I need, but how do I then
> put these new coefficients back in the model so I can use the predict
> function?
>
> my_model <- lm(x ~ . , data=my_data)
> my_scores <- predict(my_model, my_data)
>
> my_coeffs <- coef(my_model)
>
> ## here we manipulate my_coeffs
> ## and then want to set the my_model
> ## coefficients to the new values so we
> ## predict using the new values
>
> my_model.coefs <- my_coeffs ?? how is this done?
>
> ?? so that this will work with the new coefficients
> my_scores_new <- predict(my_model, my_data)
>
> Any code snippets would be appreciated very much.
Have you considered setting the coefficients to the values in
my_coeffs using offset()?
fm1 <- lm(Sepal.Length ~ offset(0.90*Sepal.Width) +
offset(0.50*Petal.Length) +
offset(-0.50*Petal.Width),
data = iris)
summary(fm1)
predict(fm1)
all.equal(as.vector(predict(fm1)),
c(as.matrix(cbind(1, iris[,2:4])) %*%
c(1.8124, 0.9, 0.5, -0.5)))
[1] TRUE
?offset
--
Chuck Cleland, Ph.D.
NDRI, Inc. (www.ndri.org)
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New York, NY 10010
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