R: Index for evaluation of step functions.

sindex {prodlim} | R Documentation

## 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)

### 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

    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)]

[Package prodlim version 2018.04.18 Index]