Re: [R] xyplot: adding pooled regression lines to a paneled type="r" plot

From: Deepayan Sarkar <deepayan.sarkar_at_gmail.com>
Date: Tue, 22 Jun 2010 12:32:50 -0700

On Tue, Jun 22, 2010 at 9:30 AM, Michael Friendly <friendly_at_yorku.ca> wrote:
> Consider the following plot that shows separate regression lines ~ age for
> each subject in the Pothoff-Roy Orthodont data,
> with separate panels by Sex:
>
> library(nlme)
> #plot(Orthodont)
> xyplot(distance ~ age|Sex, data=Orthodont, type='r', groups=Subject,
> col=gray(.50),
>   main="Individual linear regressions ~ age")
>
> I'd like to also show in each panel the pooled OLS regression line for each
> Sex in the corresponding panel,
> generated by the following model:
>
> Ortho.OLS <- lm(distance ~ age * Sex, data=Orthodont)
>
> Sex is a factor, with Male=0, so the coefficients are:
>> coef(Ortho.OLS)
>  (Intercept)           age     SexFemale age:SexFemale
>  16.3406250     0.7843750     1.0321023    -0.3048295
>
> I anticipate wanting to fit other models to these data, and also displaying
> the model-predicted
> regression lines in the same or similar plot, e.g., for a simple linear
> mixed model:
>
> Ortho.MLM <- lme(distance ~ age * Sex, data=Orthodont,
>       random = ~ 1 + age | Subject,
>       correlation = corAR1 (form = ~ 1 | Subject))

Have a look at

http://user2007.org/program/presentations/sarkar.pdf

-Deepayan



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