Icens: Fits a regression model to interval censored data.

In Epi: Statistical Analysis in Epidemiology

Fits a regression model to interval censored data.

Description

The models fitted assumes a piecewise constant baseline rate in intervals specified by the argument breaks, and for the covariates either a multiplicative relative risk function (default) or an additive excess risk function.

Usage

  Icens(first.well, last.well, first.ill,
        formula, model.type = c("MRR", "AER"), breaks,
        boot = FALSE, alpha = 0.05, keep.sample = FALSE,
        data)
## S3 method for class 'Icens'
summary(object, scale = 1, ...)
## S3 method for class 'Icens'
print(x, scale = 1, digits = 4, ...)
  

Arguments

first.well	Time of entry to the study, i.e. the time first seen without event. Numerical vector.
last.well	Time last seen without event. Numerical vector.
first.ill	Time first seen with event. Numerical vector.
formula	Model formula for the log relative risk.
model.type	Which model should be fitted.
breaks	Breakpoints between intervals in which the underlying timescale is assumed constant. Any observation outside the range of breaks is discarded.
boot	Should bootstrap be performed to produce confidence intervals for parameters. If a number is given this will be the number of bootsrap samples. The default is 1000.
alpha	1 minus the confidence level.
keep.sample	Should the bootstrap sample of the parameter values be returned?
data	Data frame in which the times and formula are interpreted.
object	an Icens object.
x	an Icens object.
scale	scaling factor for rates.
digits	how many digits is used for printing results.
...	Other parameters passed on.

Details

The model is fitted by calling either fit.mult or fit.add.

Value

An object of class "Icens": a list with three components:

rates	A glm object from a binomial model with log-link, estimating the baseline rates, and the excess risk if "AER" is specfied.
cov	A glm object from a binomial model with complementary log-log link, estimating the log-rate-ratios. Only if "MRR" is specfied.
niter	Nuber of iterations, a scalar
boot.ci	If boot=TRUE, a 3-column matrix with estimates and 1-alpha confidence intervals for the parameters in the model.
sample	A matrix of the parameterestimates from the bootstrapping. Rows refer to parameters, columns to bootstrap samples.

Author(s)

Martyn Plummer, [e-mail], Bendix Carstensen, [e-mail]

References

B Carstensen: Regression models for interval censored survival data: application to HIV infection in Danish homosexual men. Statistics in Medicine, 15(20):2177-2189, 1996.

CP Farrington: Interval censored survival data: a generalized linear modelling approach. Statistics in Medicine, 15(3):283-292, 1996.

See Also

fit.add fit.mult

Examples

data( hivDK )
# Convert the dates to fractional years so that rates are
# expressed in cases per year
for( i in 2:4 ) hivDK[,i] <- cal.yr( hivDK[,i] )

m.RR <- Icens( entry, well, ill,
               model="MRR", formula=~pyr+us, breaks=seq(1980,1990,5),
               data=hivDK)
# Currently the MRR model returns a list with 2 glm objects.
round( ci.lin( m.RR$rates ), 4 )
round( ci.lin( m.RR$cov, Exp=TRUE ), 4 )
# There is actually a print method:
print( m.RR )

m.ER <- Icens( entry, well, ill,
               model="AER", formula=~pyr+us, breaks=seq(1980,1990,5),
               data=hivDK)
# There is actually a print method:
print( m.ER )
  

Epi documentation built on Oct. 1, 2024, 5:07 p.m.