markVisits {epicalc}R Documentation

Mark visits of subjects in a long format

Description

Mark visits of subjects in a longitudinal data frame

Usage

markVisits(id, time)

Arguments

id subject identification field
time time of visit

Details

Visit numbers are essential in longitudinal data analysis. This function make it easy for R user to do so

Note

This was created from combination of the functions 'rle' and 'sapply'

Author(s)

Virasakdi Chongsuvivatwong <cvirasak@medicine.psu.ac.th>

See Also

'rle', 'sapply'

Examples

## Data frame
data(Sitka, package="MASS")
use(Sitka)

## Classical R methods
list1 <- rle(tree)
list1
visit1 <- unlist(sapply(X=list1$lengths, FUN=function(x) 1:x, simplify=FALSE))
visit1

## Do it again by Epicalc
visit2 <- markVisits(id=tree, time=Time)
visit2

[Package epicalc version 2.9.0.1 Index]