string 在 R 中的另一个字符串中查找一个字符串
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Find a string in another string in R
提问by user2498657
I want to find a string within another string in R. The strings are as follows. I want to be able to match string a to string b as and the out put should be a == bwhich returns TRUE
我想在 R 中的另一个字符串中找到一个字符串。字符串如下。我希望能够将字符串 a 与字符串 b 匹配，输出应该是a == b返回 TRUE
a <- "6250;7250;6251"
b <- "7250"
a == b #FALSE
回答by A5C1D2H2I1M1N2O1R2T1
You can use regmatchesand gregexpr, but your question is somewhat vague at the moment, so I'm not positive that this is what you're looking for:
您可以使用regmatchesand gregexpr，但目前您的问题有些含糊，所以我不确定这就是您要寻找的内容：
> regmatches(a, gregexpr(b, a))
[[1]]
[1] "7250"
> regmatches(a, gregexpr(b, a), invert=TRUE)
[[1]]
[1] "6250;" ";6251"
Based on your updated question, you're probably looking for grepl.
根据您更新的问题，您可能正在寻找grepl.
> grepl(b, a)
[1] TRUE
> grepl(999, a)
[1] FALSE
^^ We're essentially saying "look for 'b' in 'a'".
^^ 我们实际上是在说“在‘a’中寻找‘b’”。
回答by Greg Snow
If b were to equal 725instead of 7250, would you still want the result to be TRUE?
如果 b 等于725而不是7250，您还希望结果是TRUE吗？
If so then the greplanswer already given will work (and you could speed it up a bit by setting fixed=TRUEsince there are no patterns to be matched.
如果是这样，那么grepl已经给出的答案将起作用（并且您可以通过设置加快速度，fixed=TRUE因为没有要匹配的模式。
If you only want TRUEwhen there is an exact match to something between ;then you will either need to embed binto a regular expression (sprintfmay be of help), or simpler, use strsplitto split ainto just the parts to be matched, then use %in%to see if bis a match to any of those values.
如果您只想要TRUE与两者之间的某些内容完全匹配，;那么您要么需要嵌入b正则表达式（sprintf可能会有所帮助），或者更简单，用于strsplit拆分a为仅要匹配的部分，然后用于%in%查看是否b与这些值中的任何一个匹配。
