markVisits {epicalc} | R Documentation |
Mark visits of subjects in a longitudinal data frame
markVisits(id, time)
id |
subject identification field |
time |
time of visit |
Visit numbers are essential in longitudinal data analysis. This function make it easy for R user to do so
This was created from combination of the functions 'rle' and 'sapply'
Virasakdi Chongsuvivatwong <cvirasak@medicine.psu.ac.th>
'rle', 'sapply'
## 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