I have never used the data.table package. I am trying to do the following
SQL left join in R
create table all as select a.*
from dates b left outerjoin activitycount a on
a.tdate=b.tdate
and a.activity=b.activity
I found the following example but cannot figure out the syntax:
le <- Y[X]
mallx <- merge(X,Y, all.x = T)
# the column order is different so change to be the same as `merge`
setcolorder(le, names(mallx))
identical(le,mallx)
# [1] TRUE
Can anyone help? Thanks.
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