isec {Epi}R Documentation

Determine the intersection between follow-up intervals and a fixed interval.

Description

For a given piece of follow-up for ach person, this function determines the part of the follow-up which is inside a pre-specified interval. The function may occasionally be useful but is mainly included as a tool to be used in the function Lexis.

Usage

  isec( enter, exit, fail = 0, int, cens.value = 0,
        Expand = 1:length(enter))

Arguments

enter Numereical vector of entry times.
exit Numerical vector of exit times.
fail Vector of exit status, i.e. status at time exit
int The fixed interval. Numerical vector of length 2.
cens.value Censoring value. Numerical. If the person survives the fixed interval, this will be the value of the status indicator, Fail
Expand Person id to be carried to the output

Value

A matrix with columns Expand - person identification, Enter - date of entry into the interval, Exit - date of exit from the interval and Fail - status indicator.

Author(s)

Bendix Carstensen, Steno Diabetes Center, bxc@steno.dk, www.biostat.ku.dk/~bxc

See Also

Lexis, icut, fcut1, fcut, ex1

Examples

one <- round( runif( 15, 0, 15 ), 1 )
two <- round( runif( 15, 0, 15 ), 1 )
doe <- pmin( one, two )
dox <- pmax( one, two )
# Goofy data rows to test possibly odd behaviour
doe[1:3] <- dox[1:3] <- 8
dox[2] <- 6
dox[3] <- 7.5
# Some failure indicators
fail <- sample( 0:1, 15, replace=TRUE, prob=c(0.7,0.3) )
# So what have we got?
data.frame( doe, dox, fail )
# Find intersection with interval (4,8)
isec( doe, dox, fail, int=c(4,8) )
# See how it compares to original data
merge( data.frame( Expand=1:15, doe, dox, fail ),
       data.frame( isec( doe, dox, fail, int=c(4,8) ) ), all=TRUE )
  

[Package Epi version 0.7.0 Index]