frailtySurv (version 1.3.8)

drs: Diabetic Retinopathy Study (DRS)

Description

The Diabetic Retinopathy Study (DRS) was performed to determine whether the onset of blindness in 197 high-risk diabetic patients could be delayed by laser treatment. The treatment was administered to one randomly-selected eye in each patient, leaving the other eye untreated. Thus, there are 394 observations, which are clustered by patient since the level of risk will tend to vary between patients. A failure occurred when visual acuity dropped to below 5/200. All patients had a visual acuity of at least 20/100 at the beginning of the study.

Usage

data("drs")

Format

A data frame with 394 rows and 8 columns. There are two rows for each subject, one row for each eye:

subject_id

unique identifier for each subject

eye

subject's eye, where 1=right and 2=left

time

the observed follow-up time

status

outcome at the end of the observation period, where 1=blindness and 0 indicates censorship

treated

a binary covariate, where 1=treated or 0=untreated

age_at_onset

age (in years) at the onset of diabetes

laser_type

type of laser used for treatment, where 1=xenon, 2=argon

diabetes_type

type of diabetes, where 1=juvenile (age at dx < 20) and 2=adult

Examples

if (FALSE) {
data(drs)

# Clustered by subject
fit.drs <- fitfrail(Surv(time, status) ~ treated + cluster(subject_id), 
                    drs, frailty="gamma")

fit.drs

# Variance estimates
vcov(fit.drs)

# Plot the estimated cumulative baseline hazard
plot(fit.drs, type="cumhaz")
}