a <- data.frame(sid=1:3, age=c(20,30,40))
b <- data.frame(sid=c(1,2,2), bp=c(120,130,140))
d <- data.frame(sid=c(1,3,4), wt=c(170,180,190))
all <- Merge(a, b, d, id = ~ sid)
all
## Not run:
# # For data.table, first file must be the master file and must
# # contain all ids that ever occur. ids not in the master will
# # not be merged from other datasets.
# require(data.table)
# a <- data.table(a); setkey(a, sid)
# # data.table also does not allow duplicates without allow.cartesian=TRUE
# b <- data.table(sid=1:2, bp=c(120,130)); setkey(b, sid)
# d <- data.table(d); setkey(d, sid)
# all <- Merge(a, b, d)
# all
# ## End(Not run)
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