strata {survival4}R Documentation

Identify strata variables.

Description

The result is identical to the interaction() function, but for the labeling of the factors (strata is more verbose).

Usage

strata(..., na.group=F)

Arguments

... Any number of variables. All must be the same length.
na.group if set to T, then missing values are treated as a distinct level of each variable.

Value

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

See Also

coxph

Examples

data(ovarian)
coxph(Surv(futime, fustat) ~ age + strata(rx))


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