Hi,
probably just a quick question: can I somehow change the formula used with
predict? E.g., the regression was run on y ~ u + v + w but for the prediction
the term v should be removed from the formula contained in the regression
object and only y ~ u + w be used.
I could use model.matrix
Try this;
mod1 - lm(y ~ u + v + w, data = d)
update(mod1, . ~ . -v)
On Tue, Jan 19, 2010 at 2:10 PM, Werner W. pensterfuz...@yahoo.de wrote:
Hi,
probably just a quick question: can I somehow change the formula used with
predict? E.g., the regression was run on y ~ u + v + w but for the
This recomputes the lm but if that is ok then:
mod - lm(y1 ~ x1 + x2 + x3 + x4, anscombe)
mod$call$formula - update(as.formula(mod$call$formula), ~ . - x1 - x2)
predict(eval(mod$call), list(x3 = 1, x4 = 1))
On Tue, Jan 19, 2010 at 11:10 AM, Werner W. pensterfuz...@yahoo.de wrote:
Hi,
Werner,
You could set 0 to that regressors you don't want to consider for
prediction.
da - expand.grid(A=1:20, B=rnorm(20, 4, 0.2), C=10^seq(1,2,l=20))
da$y - rnorm(da$A, 0, 0.3)
m0 - lm(y~A+B+C, data=da)
new - da
new$C - 0
predict(m0)[1:5]
predict(m0, newdata=new)[1:5]
At your disposal.
Thanks Gabor and Henrique!
Sorry for the imprecise question. I want predict() to use the coefficients
estimated by the original regression but to exclude terms from the
prediction formula. If I originally estimated y ~ x1 + x2 and got
coefficients b0, b1, b2, I would like to remove x2 and
On Jan 19, 2010, at 12:05 PM, werner w wrote:
Thanks Gabor and Henrique!
Sorry for the imprecise question. I want predict() to use the
coefficients
estimated by the original regression but to exclude terms from the
prediction formula. If I originally estimated y ~ x1 + x2 and got
If you want to keep the same coefficients but ignore certain ones just
use 0 for the ones you don't want:
mod - lm(Sepal.Length ~ Petal.Length + Petal.Width, iris)
predict(mod, list(Petal.Length = 3, Petal.Width = 0))
Regarding the problem with the example, the example data was not the
best for
Thanks a lot for the answers!
Somehow I thought there will be a facility to modify the formula. But
setting unwanted variables to zero will of course work and maybe is simple
enough. Thanks again!
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