R: Epileptic Seizure Data

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. 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)

[Package flexmix version 2.3-14 Index]