ex1 {Epi}R Documentation

Split follow-up time along a timescale

Description

Splits follow-up time at prespecified points of follow-up.

Usage

ex1( enter, exit, fail, origin = 0, scale = 1, breaks,
     data = data.frame(enter, exit, fail),
     Expand = 1:nrow(data) )

Arguments

enter Date of entry einto the study (start of follow-up). Numeric.
exit Date of termination of follow-up. Numeric.
fail Status at exit from the study.
origin Origin of the timescale to split on. Specified on the input timescale, i.e. that of enter and exit.
scale Scaling between input and analysis timescale.
breaks Breakpoints on the analysis timescale. Follow-up before min(breaks) and and ater max(breks) is discarded.
data Dataframe of variables to carry over to the output.
Expand Variable identifying original records.

Details

If entry and exit are given in days (for example as Date variables, and we want follow-up cut at 5-year age intervals, the we should choose origin equal to bithdate, scale equal to 365.25 and breaks as seq(0,100,5). Thus the input timescale is calendar tiem measured in days, and output timescale is age measured in years.

Value

A dataframe with one row per follow-up interval, and variables as in data, preceded by the variables:

Expand Identification of the rows from the input dataframe.
Enter Entry date for the interval.
Exit Exit date for the interval.
Fail Failure indicator for end of the current interval.

Author(s)

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

See Also

Lexis, isec, icut, fcut1, ex1

Examples

one <- round( runif( 15, 0, 10 ), 1 )
two <- round( runif( 15, 0, 10 ), 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) )
# Split follow-up:
ex1( doe, dox, fail, breaks=0:10 )

[Package Epi version 0.6.0 Index]