data.table (version 1.15.4)

setops: Set operations for data tables


Similar to base R set functions, union, intersect, setdiff and setequal but for data.tables. Additional all argument controls how duplicated rows are handled. Functions fintersect, setdiff (MINUS or EXCEPT in SQL) and funion are meant to provide functionality of corresponding SQL operators. Unlike SQL, data.table functions will retain row order.


fintersect(x, y, all = FALSE)
fsetdiff(x, y, all = FALSE)
funion(x, y, all = FALSE)
fsetequal(x, y, all = TRUE)


A data.table in case of fintersect, funion and fsetdiff. Logical TRUE or FALSE for fsetequal.


x, y



Logical. Default is FALSE and removes duplicate rows on the result. When TRUE, if there are xn copies of a particular row in x and yn copies of the same row in y, then:

  • fintersect will return min(xn, yn) copies of that row.

  • fsetdiff will return max(0, xn-yn) copies of that row.

  • funion will return xn+yn copies of that row.

  • fsetequal will return FALSE unless xn == yn.


bit64::integer64 columns are supported but not complex and list, except for funion.


See Also

data.table, rbindlist,, unique, duplicated, uniqueN, anyDuplicated


Run this code
x = data.table(c(1,2,2,2,3,4,4))
x2 = data.table(c(1,2,3,4)) # same set of rows as x
y = data.table(c(2,3,4,4,4,5))
fintersect(x, y)            # intersect
fintersect(x, y, all=TRUE)  # intersect all
fsetdiff(x, y)              # except
fsetdiff(x, y, all=TRUE)    # except all
funion(x, y)                # union
funion(x, y, all=TRUE)      # union all
fsetequal(x, x2, all=FALSE) # setequal
fsetequal(x, x2)            # setequal all

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