match and %in% for Arrow objects

Source: R/compute.R

base::match() is not a generic, so we can't just define Arrow methods for it. This function exposes the analogous functions in the Arrow C++ library.

match_arrow(x, table, ...)

is_in(x, table, ...)

Arguments

x

Scalar, Array or ChunkedArray
table

Scalar, Array, ChunkedArray`, or R vector lookup table.
...

additional arguments, ignored

Value

match_arrow() returns an int32-type Arrow object of the same length and type as x with the (0-based) indexes into table. is_in() returns a boolean-type Arrow object of the same length and type as x with values indicating per element of x it it is present in table.

Examples

# note that the returned value is 0-indexed
cars_tbl <- Table$create(name = rownames(mtcars), mtcars)
match_arrow(Scalar$create("Mazda RX4 Wag"), cars_tbl$name)

#> Scalar
#> 1

is_in(Array$create("Mazda RX4 Wag"), cars_tbl$name)

#> Array
#> <bool>
#> [
#>   true
#> ]

# Although there are multiple matches, you are returned the index of the first 
# match, as with the base R equivalent
match(4, mtcars$cyl) # 1-indexed

#> [1] 3
match_arrow(Scalar$create(4), cars_tbl$cyl) # 0-indexed

#> Scalar
#> 2

# If `x` contains multiple values, you are returned the indices of the first 
# match for each value.
match(c(4, 6, 8), mtcars$cyl)

#> [1] 3 1 5
match_arrow(Array$create(c(4, 6, 8)), cars_tbl$cyl)

#> Array
#> <int32>
#> [
#>   2,
#>   0,
#>   4
#> ]

# Return type matches type of `x`
is_in(c(4, 6, 8), mtcars$cyl) # returns vector

#> Array
#> <bool>
#> [
#>   true,
#>   true,
#>   true
#> ]
is_in(Scalar$create(4), mtcars$cyl) # returns Scalar

#> Scalar
#> true
is_in(Array$create(c(4, 6, 8)), cars_tbl$cyl) # returns Array

#> Array
#> <bool>
#> [
#>   true,
#>   true,
#>   true
#> ]
is_in(ChunkedArray$create(c(4, 6), 8), cars_tbl$cyl) # returns ChunkedArray

#> ChunkedArray
#> [
#>   [
#>     true,
#>     true
#>   ],
#>   [
#>     true
#>   ]
#> ]