计算字符串中模式匹配的数量 [英] Count the number of pattern matches in a string

问题描述

例如，我有一个字符串

"AAAAAAACGAAAAAACGAAADGCGEDCG"

我想统计"CG"重复了多少次.我该怎么做?

I want to count how many times "CG" is repeated. How do I do that?

推荐答案

你可以使用gregexpr来查找vec中"CG"的位置代码>.我们必须检查是否没有匹配(-1).函数 sum 计算匹配的数量.

You can use gregexpr to find the positions of "CG" in vec. We have to check whether there was no match (-1). The function sum counts the number of matches.

> vec <- "AAAAAAACGAAAAAACGAAADGCGEDCG"
> sum(gregexpr("CG", vec)[[1]] != -1)
[1] 4

如果你有一个字符串向量，你可以使用sapply:

If you have a vector of strings, you can use sapply:

> vec <- c("ACACACACA", "GGAGGAGGAG", "AACAACAACAAC", "GGCCCGCCGC", "TTTTGTT", "AGAGAGA")
> sapply(gregexpr("CG", vec), function(x) sum(x != -1))
[1] 0 0 0 2 0 0

如果你有一个字符串列表，你可以使用 unlist(vec) 然后使用上面的解决方案.

If you have a list of strings, you can use unlist(vec) and then use the solution above.

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