Description Usage Arguments Details Value See Also Examples

This is a special function used in the context of the Cox survival model. It identifies stratification variables when they appear on the right hand side of a formula.

1 |

`...` |
any number of variables. All must be the same length. |

`na.group` |
a logical variable, if |

`shortlabel` |
if |

`sep` |
the character used to separate groups, in the created label |

When used outside of a `coxph`

formula the result of the function
is essentially identical to the `interaction`

function,
though the labels from `strata`

are often more verbose.

a new factor, whose levels are all possible combinations of the factors supplied as arguments.

1 2 3 4 5 6 |

```
[1] "1" "2" "3" "4"
[1] "low, 1" "low, 2" "low, 3" "low, 4" "medium, 1" "medium, 2"
[7] "medium, 3" "medium, 4" "high, 1" "high, 2" "high, 3" "high, 4"
Call:
coxph(formula = Surv(futime, fustat) ~ age + strata(rx), data = ovarian)
coef exp(coef) se(coef) z p
age 0.1374 1.1472 0.0474 2.9 0.0038
Likelihood ratio test=12.7 on 1 df, p=0.000368
n= 26, number of events= 12
```

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