prodlim (version 2023.08.28)

sindex: Index for evaluation of step functions.

Description

Returns an index of positions. Intended for evaluating a step function at selected times. The function counts how many elements of a vector, e.g. the jump times of the step function, are smaller or equal to the elements in a second vector, e.g. the times where the step function should be evaluated.

Usage

sindex(jump.times, eval.times, comp = "smaller", strict = FALSE)

Value

Index of the same length as eval.times containing the numbers of the jump.times that are smaller than or equal to eval.times.

Arguments

jump.times

Numeric vector: e.g. the unique jump times of a step function.

eval.times

Numeric vector: e.g. the times where the step function should be evaluated

comp

If "greater" count the number of jump times that are greater (greater or equal when strict==FALSE) than the eval times

strict

If TRUE make the comparison of jump times and eval times strict

Author

Thomas A. Gerds

Details

If all jump.times are greater than a particular eval.time the sindex returns 0. This must be considered when sindex is used for subsetting, see the Examples below.

Examples

test <- list(time = c(1, 1,5,5,2,7,9),
		status = c(1,0,1,0,1,1,0))
fit <- prodlim(Hist(time,status)~1,data=test)
jtimes <- fit$time
etimes <- c(0,.5,2,8,10)
fit$surv
c(1,fit$surv)[1+sindex(jtimes,etimes)]