[R] Marginal effects from interaction regression model
Michael Friendly
friendly at yorku.ca
Mon Jul 26 15:08:42 CEST 2010
The plots you are looking for are called 'effect plots'. See the
effects package by John Fox.
Guillem R. wrote:
> As far as I know, the predict command gives the predicted values (and
> intervals) of y, but what I'm looking for is the conditional effects (betas)
> of x on y conditional on values of z.
>
> I'm trying to produce a plot similar to the first shown in this link:
> http://homepages.nyu.edu/~mrg217/interaction.html#code
>
> Thanks again
>
>
>
> David Winsemius wrote:
>>
>> On Jul 25, 2010, at 10:24 PM, Guillem R. wrote:
>>
>>> Dear all,
>>>
>>> I'd like to plot the marginal effect of a variable in a multiplicative
>>> interaction regression, that is, the effect of a variable
>>> conditional on the
>>> values of another variable. As an illustration, given model lm1
>>>
>>> lm1 <- lm(y ~ x*z)
>> ? predict
>>
>> Perhaps:
>>
>> predict(lm1, newdata=data.frame(x=1:10, z=5), interval="confidence")
>>
>>
>>> I'd like to get the effects of x on y conditional on the values of
>>> z, with
>>> the corresponding confidence intervals if possible. Does anyone know
>>> of any
>>> package or simple way to do this?
>>>
>>> Thanks
>> --
>>
>> David Winsemius, MD
>> West Hartford, CT
>>
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>>
>>
>
--
Michael Friendly Email: friendly AT yorku DOT ca
Professor, Psychology Dept.
York University Voice: 416 736-5115 x66249 Fax: 416 736-5814
4700 Keele Street Web: http://www.datavis.ca
Toronto, ONT M3J 1P3 CANADA
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