seizure {flexmix} | R Documentation

## 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")

### Format

A data frame with 140 observations on the following 4 variables.

Seizures
  A numeric vector, daily counts of epileptic seizures.
Hours
  A numeric vector, hours of daily parental observation.
Treatment
  A factor with levels `No` and `Yes`.
Day
  A numeric vector.

### Source

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

### References

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

### Examples

    data("seizure")
    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)

[Package flexmix version 2.2-4 Index]