Reshaping data in R with “login” “logout” times

Question

I\'m new to R, and am working on a side project for my own purposes. I have this data (reproducable dput of this is at the end of the question):

     X              


        

Answer 1

Base version:

samp$count <- with(samp, ave(as.character(user),list(state,user),FUN=seq_along) )

out <- merge(
  samp[samp$state=="joined",c("user","datetime","count")],
  samp[samp$state=="left",c("user","datetime","count")],
  by=c("user","count"), all.x=TRUE
)

out[order(out$count),]