to_r: Export data to R

Description

Export C++ data to an R object.

Usage

to_r(x, n = NULL, from = NULL, to = NULL)

Value

Returns a vector in case of CppSet, CppUnorderedSet, CppMultiset, CppUnorderedMultiset, CppStack, CppQueue, CppPriorityQueue, CppVector, CppDeque, CppForwardList, and CppList objects. Returns a data frame in case of CppMap, CppUnorderedMap, CppMultimap, and CppUnorderedMultimap objects.

Arguments

x: A cppcontainers object.
n: The number of elements to export. If n is positive it exports elements starting at the front of the container. If n is negative, it starts at the back. Negative values only work on CppSet, CppMultiset, CppMap, CppMultimap, CppVector, CppDeque, and CppList objects.
from: The first value in CppSet, CppMultiset, CppMap, CppMultimap objects to export. If it is not a member of x, the export starts at the subsequent value. In a CppVector or CppDeque object, from marks the index of the first element to export. Ignored for other classes.
to: The last value in CppSet, CppMultiset, CppMap, CppMultimap objects to export. If it is not a member of x, the export ends with the prior value. In a CppVector or CppDeque object, from marks the index of the last element to export. Ignored for other classes.

Details

to_r has side effects, when applied to stacks, queues, or priority queues. These container types are not iterable. Hence, to_r removes elements from the CppStack, CppQueue, and CppPriorityQueue objects when exporting them to R. When n is specified, the method removes the top n elements from a stack or priority queue or the first n elements from a queue. Otherwise, it removes all elements. Other container types, like sets, etc., are unaffected.

Examples

Run this code

s <- cpp_set(11:20)
to_r(s)
# [1] 11 12 13 14 15 16 17 18 19 20

to_r(s, n = 4)
# [1] 11 12 13 14

to_r(s, n = -4)
# [1] 20 19 18 17

to_r(s, from = 14)
# [1] 14 15 16 17 18 19 20

to_r(s, to = 18)
# [1] 11 12 13 14 15 16 17 18

to_r(s, from = 14, to = 18)
# [1] 14 15 16 17 18

m <- cpp_unordered_multimap(c("hello", "hello", "there"), 4:6)
to_r(m)
#     key value
# 1 there     6
# 2 hello     4
# 3 hello     5

s <- cpp_stack(11:20)
to_r(s, n = 3)
# [1] 20 19 18
s
# Top element: 17