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Union

WMA link

Union[a, b, ...]

gives the union of the given set or sets. The resulting list will be sorted and each element will only occur once.

A union of two lists:

• • Union[{a, b, c}, {c, d, e}]

A union of two associations:

• • Union[{a -> b}, {c -> d}]

A union of one item is the item. Note that the list is sorted:

• • Union[{c, b, a}]

As usual, Union removes duplicate values:

• • Union[{5, 1, 3, 7, 1, 8, 3}]

Union using a custom test which compares using the last coordinate of each element list:

• • Union[{{a, 1}, {b, 2}}, {{c, 1}, {d, 3}}, SameTest->(SameQ[Last[#1],Last[#2]]&)]

• • Union[{1, 2, 3}, {2, 3, 4}, SameTest->Less]