A wrapper function to summarize 2-group and grey-zone (3-group) models with *R^2* and c-index after fitting Cox regression.

1 | ```
cox.summary(stime, sind, var)
``` |

`stime` |
A nx1 vector of survival time |

`sind` |
A nx1 vector of censoring indicator |

`var` |
A nx1 vector of risk groupings to correlate with survival. For the 2-group and 3-group models, it is a categorical vector |

It returns a vector with components such as the p value from fitting a Cox regression model, AIC (Akaike information criterion), and the c-index [1, 2], *R^2* from the XO method [3], the OXS method [4] and the Nagelkerke method.

Harrell F, Califf R, Pryor D, Lee K and Rosati R. Evaluating the yield of medical tests. *JAMA: The Journal of the American Medical Association* 1982; 247(18):2543-2546.

Harrell F, Lee K, Califf R, Pryor D and Rosati R. Regression modeling strategies for
improved prognostic prediction. *Statistics in Medicine* 1984; 3(2):143-152.

Xu R and O'Quigley J. A *R^2* type measure of dependence for proportional hazards models. *Nonparametric Statistics* 1999; 12:83-107.

O'Quigley J, Xu R and Stare J. Explained randomness in proportional hazards models. *Statistics in Medicine* 2005; 24:479-489.

1 | ```
#See Examples for greyzone.func in this package.
``` |

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