Index for evaluation of step functions.

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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

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

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

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.

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.

Author(s)

Thomas A. Gerds tag@biostat.ku.dk

Examples

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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)]

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