# [R] How to get predicted values of y for different x values?

David Winsemius dwinsemius at comcast.net
Tue Jul 19 21:14:58 CEST 2011

```On Jul 19, 2011, at 2:36 PM, Jeff Newmiller wrote:

> ?predict
>
> Use data.frame() to generate input vectors (newdata) for which you
> want predicted values.

The OP probably needs to use expand.grid to generate the spanning
combinations of x values. He will in addition need to include values
for "control" variables.

dfrm <- expand.grid(x1 = 0: 6, x2 = 0: 5,  x3 = 0 : 4)
dfrm\$control1 <- <some value of same class as original control1 data>
repeat x 2

--
David.
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> Sent from my phone. Please excuse my brevity.
>
> halptekin <halptekin at gmail.com> wrote:
>
> Here is my model with interaction terms and control variables (I
> changed
> variables names for easy read):
>
> reg1 <- lm(y ~ x1*x2*x3 +control1 + control2 + control3)
>
> x1 ranges from 0 to 6; x2 from 0 to 5; and x3 from 0 to 4. All three
> are
> discrete ordinal variables; but I will treat them as continuous
> variables.
>
> (a) How can I see the predicted values of y for each of these
> scenarios (210
> scenarios I guess)?
> (b) How can I see the predicted value of y for the minimum and maximum
> values of x1, x2, and x3 (8 scenarios)?
> (c) How can I see the predicted value of y for x1=6; x2=5; and x3=4 (1
> scenario)?
>
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