Abstract
For right-censored data perhaps the most commonly used tests are weighted logrank tests, such as the logrank and Wilcoxon-type tests. In this paper we review several generalizations of those weighted logrank tests to interval-censored data and present an R package, interval, to implement many of them. The interval package depends on the perm package, also presented here, which performs exact and asymptotic linear permutation tests. The perm package performs many of the tests included in the already available coin package, and provides an independent validation of coin. We review analysis methods for interval-censored data, and we describe and show how to use the interval and perm packages.
Highlights
In their original paper introducing the logrank test, Peto and Peto (1972) outlined how to perform permutation-based logrank tests for interval-censored data
In this paper we describe an R package, called interval, to perform weighted logrank tests (WLRT) for intervalcensored data
This application section demonstrates the use of two main functions of interval: icfit which provide nonparametric maximum likelihood estimators (NPMLEs) of the survival distribution and ictest which performs weighted logrank tests
Summary
In their original paper introducing the logrank test, Peto and Peto (1972) outlined how to perform permutation-based logrank tests for interval-censored data. We know of no readily available software to perform these tests (or other different generalizations of the WLRTs to intervalcensored data), except for the S-PLUS functions (written by the first author) upon which the interval package is based (Fay 1999b). This application section demonstrates the use of two main functions of interval: icfit which provide nonparametric maximum likelihood estimators (NPMLEs) of the survival distribution and ictest which performs weighted logrank tests. All implementations of the WLRTs require first fitting an NPMLE of the overall survival distribution and, for some kinds of inferences, permutation methods may be used Because of this latter fact, the interval depends on the perm package which performs exact and asymptotic linear permutation tests. We show how the wlr_trafo function of the interval package may be called seamlessly from within coin to perform exact permutation tests on interval-censored data possibly more quickly than using the default perm package
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