Epilepsy Attacks Data Set

Description

Data from a clinical trial of 59 patients with epilepsy (Breslow, 1996) in order to illustrate diagnostic techniques in Poisson regression.

Usage

data(epilepsy, package="robustbase")

Format

A data frame with 59 observations on the following 11 variables.

ID

Patient identification number

Y1

Number of epilepsy attacks patients have during the first follow-up period

Y2

Number of epilepsy attacks patients have during the second follow-up period

Y3

Number of epilepsy attacks patients have during the third follow-up period

Y4

Number of epilepsy attacks patients have during the forth follow-up period

Base

Number of epileptic attacks recorded during 8 week period prior to randomization

Age

Age of the patients

Trt

a factor with levels placebo progabide indicating whether the anti-epilepsy drug Progabide has been applied or not

Ysum

Total number of epilepsy attacks patients have during the four follow-up periods

Age10

Age of the patients devided by 10

Base4

Variable Base devided by 4

Details

Thall and Vail reported data from a clinical trial of 59 patients with epilepsy, 31 of whom were randomized to receive the anti-epilepsy drug Progabide and 28 of whom received a placebo. Baseline data consisted of the patient's age and the number of epileptic seizures recorded during 8 week period prior to randomization. The response consisted of counts of seizures occuring during the four consecutive follow-up periods of two weeks each.

Source

Thall, P.F. and Vail S.C. (1990) Some covariance models for longitudinal count data with overdispersion. Biometrics 46, 657–671.

References

Diggle, P.J., Liang, K.Y., and Zeger, S.L. (1994) Analysis of Longitudinal Data; Clarendon Press.

Breslow N. E. (1996) Generalized linear models: Checking assumptions and strengthening conclusions. Statistica Applicata 8, 23–41.

Examples

data(epilepsy)
str(epilepsy)
pairs(epilepsy[,c("Ysum","Base4","Trt","Age10")])

Efit1 <- glm(Ysum ~ Age10 + Base4*Trt, family=poisson, data=epilepsy)
summary(Efit1)

## Robust Fit :
Efit2 <- glmrob(Ysum ~ Age10 + Base4*Trt, family=poisson, data=epilepsy,
                method = "Mqle",
                tcc=1.2, maxit=100)
summary(Efit2)