Epi: expand.data – R documentation

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Epi

expand.data

Function to expand data for regression analysis of interval censored data.

Description

This is a utility function.

The original records with first.well, last.well and first.ill are expanded to multiple records; several for each interval where the person is known to be well and one where the person is known to fail. At the same time columns for the covariates needed to estimate rates and the response variable are generated.

Usage

expand.data(fu, formula, breaks, data)

Arguments

`fu`	A 3-column matrix with `first.well`, `last.well` and `first.ill` in each row.
`formula`	Model fromula, used to derive the model matrix.
`breaks`	Defines the intervals in which the baseline rate is assumed constant. All follow-up before the first and after the last break is discarded.
`data`	Datafrem in which `fu` and `formula` is interpreted.

Value

Returns a list with three components

`rates.frame`	Dataframe of covariates for estimation of the baseline rates — one per interval defined by `breaks`.
`cov.frame`	Dataframe for estimation of the covariate effects. A data-framed version of the designmatrix from `formula`.
`y`	Response vector.

Author(s)

Martyn Plummer, martyn.plummer@r-project.org

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.