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))
TIA,
-Michael
--
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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