如何使用 stringr 函数替换精确的字符串? [英] How to replace an exact string using stringr functions?

问题描述

我正在尝试使用 stringr 函数替换列中的确切字符串.

I'm trying to replace exact strings in a column using stringr functions.

我试用的数据集是这样的:

The dataset I try it on is this:

data <- data.frame(
  column = c("Value", "Values", "Value", "Values")
)

data

  column
1 Value
2 Values
3 Value
4 Values

我想用值"替换值".我尝试了 str_replace(data$column, "Value", "Values")，但这会产生以下不需要的替换:

I want to replace "Value" with "Values". I tried str_replace(data$column, "Value", "Values"), but this creates the following unwanted replacements:

[1] "Values"  "Valuess" "Values"  "Valuess"

我希望输出为:

[1] "Values"  "Values" "Values"  "Values"

推荐答案

以下是使用正则表达式的几种可能性:

Here are a few possibilities using regular expressions:

x <- c("value", "values")
str_replace(x, "value$", "values") #method 1
str_replace(x, "value\\b", "values") #method 2
str_replace(x, "value(?!s)", "values") #method 3

以上所有返回相同的

[1] "values" "values"

简短说明:第一种方法在字符串末尾查找值".符号 $ 匹配字符串的结尾.

A short explanation: the first method looks for 'value' at the end of a string. The symbol $ matches the end of the string.

第二种方法查找值"，然后是单词边界.

The second method looks for 'value' followed by a word boundary.

第三种方法查找value"后跟除符号s"之外的任何内容.

The third method looks for 'value' followed by anything but the symbol 's'.

您可以找到有关 stringr 和正则表达式的有用备忘单此处.希望这会有所帮助.

You can find a helpful cheat sheet about stringr and regular expressions here. Hope this helps.

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