epilepsy: Epileptic seizure counts

Description

Breslow and Clayton (1993) analyse data initially provided by Thall and Vail (1990) concerning seizure counts in a randomised trial of anti-convulsant therapy in epilepsy. Covariates are treatment, 8-week baseline seizure counts, and age of the patients in years.

Usage

epilepsy

Arguments

Format

A dataframe of 236 observations containing information on the following 9 variables.

Age: The age of the patients in years
Base: The seizure count at 8-weeks baseline
Trt: Either 0 or 1 indicating if the patient recieved anti-convulsant therapy
log_Age_c: The logarithm of Age centered arounds its mean
log_Base4_c: The logarithm of Base divided by 4 (i.e. log(Base/4)) centered around its mean
Trt_c: Trt centered around its mean
visit: The session number from 1 (first visit) to 4 (last visit)
count: The seizure count between two visits
patient: The patient number
obs: The observation number, i.e. a unique identifier for each observation

Examples

Run this code

# NOT RUN {
## poisson regression without random effects. 
fit1 <- brm(count ~ log_Age_c + log_Base4_c * Trt_c, 
            data = epilepsy, family = poisson())
summary(fit1) 
plot(fit1)             
    
## poisson regression with random intercepts of patients and visits
## as well as normal priors for fixed effects parameters.    
fit2 <- brm(count ~ log_Age_c + log_Base4_c * Trt_c 
            + (1|patient) + (1|visit), 
            data = epilepsy, family = poisson(), 
            prior = set_prior("normal(0,5)"))
summary(fit2) 
plot(fit2)
# }
# NOT RUN {
 
# }

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