aggregate.survfit Average survival curves

Description

For a survfit object containing multiple curves, create average curves over a grouping.

Usage

## S3 method for class 'survfit'
aggregate(x, by = NULL, FUN = mean, ...)

Arguments

x	a survfit object which has a data dimension.
by	an optional list or vector of grouping elements, each as long as dim(x)['data'].
FUN	a function to compute the summary statistic of interest.
...	optional further arguments to FUN.

Details

The primary use of this is to take an average over multiple survival curves that were created from a modeling function. That is, a marginal estimate of the survival. It is primarily used to average over multiple predicted curves from a Cox model.

Value

a survfit object of lower dimension.

See Also

survfit

Examples

cfit <- coxph(Surv(futime, death) ~ sex + age*hgb, data=mgus2)
# marginal effect of sex, after adjusting for the others
dummy <- rbind(mgus2, mgus2)
dummy$sex <- rep(c("F", "M"), each=nrow(mgus2)) # population data set
dummy <- na.omit(dummy)   # don't count missing hgb in our "population
csurv <- survfit(cfit, newdata=dummy)
dim(csurv)  # 2 * 1384 survival curves
csurv2 <- aggregate(csurv, dummy$sex)