如何在R中给出单词列表中找到唯一单词

Question

我有一个单词列表

a = c("when","to","use","each","effect","","recognizing","each","effect","?",":")
a
[1] "when"        "to"          "use"         "each"       
[5] "effect"      ""            "recognizing" "each"       
[9] "effect"      "?"           ":" 

此列表可能包含数千个单词。我怎样才能有效地找出独特的单词，即＆＃34;当＆＃34; ＆＃34;至＆＃34; ＆＃34;使用＆＃34; ＆＃34;每个＆＃34; ＆＃34;效果＆＃34; ＆＃34;识别＆＃34;

我尽量避免使用for循环。

谢谢

Answer 1

unique(a)

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table(a)

Answer 2

您可以使用散列映射来维护列表而不是使用数组。它会自动保持数据的唯一性。