# coxphf

## Overview

The package coxphf implements Firth’s penalized maximum likelihood
bias reduction method for Cox regression which has been shown to provide
a solution in case of monotone likelihood (nonconvergence of likelihood
function). The program fits profile penalized likelihood confidence
intervals which were proved to outperform Wald confidence intervals.

## Installation

```
# Install coxphf from CRAN
install.packages("coxphf")
# Or the development version from GitHub:
# install.packages("devtools")
devtools::install_github("georgheinze/coxphf")
```

## Usage

The call of the main function of the library follows the structure of
the standard functions requiring a data.frame and a formula for the
model specification. The response must be a survival object as returned
by the ‘Surv’ function (see its documentation in the survival package).
The resulting object belongs to the new class coxphf.

```
library(survival)
data(breast)
fit.breast<-coxphf(data=breast, Surv(TIME,CENS)~T+N+G+CD)
summary(fit.breast)
```

## Acknowledgment

This work was supported by the Austrian Science Fund (FWF) (award I
2276).