基于正则表达式模式从向量中排除元素 [英] Exclude elements from vector based on regular expression pattern

问题描述

我有一些数据要使用 R 中的正则表达式进行清理.

I have some data which I want to clean up using a regular expression in R.

很容易找到如何获取包含某些模式或不包含某些单词(字符串)的元素，但我不知道如何排除包含模式的单元格.

It is easy to find how to get elements that contain certain patterns, or do not contain certain words (strings), but I can't find out how to do this for excluding cells containing a pattern.

如何使用通用函数来只保留那些不包含PATTERN的矢量元素?

How could I use a general function to only keep those elements from a vector which do not contain PATTERN?

我不想举个例子，因为这可能会导致人们使用其他(虽然通常很好)的方式来回答而不是预期的方式:基于正则表达式排除.无论如何，这里是:

I prefer not to give an example, as this might lead people to answer using other (though usually nice) ways than the intended one: excluding based on a regular expression. Here goes anyway:

如何排除包含以下任何字符的所有元素:'pyfgcrl

How to exclude all the elements that contain any of the following characters: 'pyfgcrl

vector <- c("Cecilia", "Cecily", "Cecily's", "Cedric", "Cedric's", "Celebes", 
            "Celebes's", "Celeste", "Celeste's", "Celia", "Celia's", "Celina")

在这种情况下，结果将是一个空向量.

The result would be an empty vector in this case.

推荐答案

从评论中，经过一些测试，人们会发现我的建议是不正确的.

From the comments, and with a little testing, one would find that my suggestion wasn't correct.

这里有两个正确的解决方案:

Here are two correct solutions:

vector[!grepl("['pyfgcrl]", vector)]                    ## kohske
grep("['pyfgcrl]", vector, value = TRUE, invert = TRUE) ## flodel

如果他们中的任何一个想要重新发布并接受他们的回答，我很乐意在这里删除我的.

If either of them wants to re-post and accept credit for their answer, I'm more than happy to delete mine here.

您正在寻找的通用函数是 grepl.来自 grepl 的帮助文件:

The general function that you are looking for is grepl. From the help file for grepl:

grepl 返回一个逻辑向量(匹配或不匹配 x 的每个元素).

grepl returns a logical vector (match or not for each element of x).

此外，您应该阅读 regex 的帮助页面，其中描述了 字符类 是什么.在本例中，您创建了一个字符类 ['pyfgcrl]，它表示要查找方括号中的任何字符.然后你可以用 ! 否定它.

Additionally, you should read the help page for regex which describes what character classes are. In this case, you create a character class ['pyfgcrl], which says to look for any character in the square brackets. You can then negate this with !.

所以，到目前为止，我们有一些看起来像:

So, up to this point, we have something that looks like:

!grepl("['pyfgcrl]", vector)

为了得到你想要的东西，你像往常一样子集.

To get what you are looking for, you subset as usual.

vector[!grepl("['pyfgcrl]", vector)]

<小时>

对于@flodel 提供的第二种解决方案，grep 默认返回匹配的 position，value = TRUE 参数让您返回实际的字符串值.invert = TRUE 表示返回不匹配的值.

---

For the second solution, offered by @flodel, grep by default returns the position where a match is made, and the value = TRUE argument lets you return the actual string value instead. invert = TRUE means to return the values that were not matched.

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