flexmix (version 2.3-9)

seizure: Epileptic Seizure Data

Description

Data from a clinical trial where the effect of intravenous gamma-globulin on suppression of epileptic seizures is studied. Daily observations for a period of 140 days on one patient are given, where the first 27 days are a baseline period without treatment, the remaining 113 days are the treatment period.

Usage

data("seizure")

source

P. Wang, M. Puterman, I. Cockburn, and N. Le. Mixed poisson regression models with covariate dependent rates. Biometrics, 52, 381--400, 1996.

References

B. Gruen and F. Leisch. Bootstrapping finite mixture models. In J. Antoch, editor, Compstat 2004 - Proceedings in Computational Statistics, 1115--1122. Physika Verlag, Heidelberg, Germany, 2004. ISBN 3-7908-1554-3.

Examples

data("seizure", package = "flexmix")
plot(Seizures/Hours~Day, col=as.integer(Treatment),
     pch=as.integer(Treatment), data=seizure)
abline(v=27.5, lty=2, col="grey")
legend(140, 9, c("Baseline", "Treatment"),
       pch=1:2, col=1:2, xjust=1, yjust=1)

set.seed(123)

## The model presented in the Wang et al paper: two components for
## "good" and "bad" days, respectively, each a Poisson GLM with hours of
## parental observation as offset

seizMix <- flexmix(Seizures~Treatment*log(Day),
                   data=seizure, k=2,
                   model=FLXMRglm(family="poisson", offset=log(seizure$Hours)))

summary(seizMix)
summary(refit(seizMix))

matplot(seizure$Day, fitted(seizMix)/seizure$Hours, type="l",
        add=TRUE, col=3:4)