R: Fits a regression model to interval censored data.

Icens {Epi} | R Documentation

## 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 )

### 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.

### 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, plummer@iarc.fr, Bendix Carstensen, b@bxc.dk

### 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 )

[Package Epi version 2.37 Index]