问题描述
这个问题似乎很琐碎，但我无法弄清楚为什么它不起作用.我只想用单个值(不包括"+"运算符)替换涉及"+"运算符的字符变量.由于某些原因，gsub()和sub()函数替换了数字值，但保留了运算符.关于如何可以克服的任何提示?非常感谢！
the question seems totally trivial but I cannot figure out why it isn't working. I simply want to replace a character variable involving a "+" operator with a single value excluding the "+" operator. For some reason gsub() and sub() function replace the number value but keep the operator. Any hint on how this can be overcome?Many thanks!
data <- c(1,2,3,4,"5+")
gsub(pattern="5+",replacement="5",x=data)
#[1] "1" "2" "3" "4" "5+"
gsub(pattern="5+",replacement="",x=data)
#[1] "1" "2" "3" "4" "+"
R 3.0.2
推荐答案
+是一个元字符，要与之匹配时需要转义:
+ is a metacharacter, and needs to be escaped when you want to match it:
gsub(pattern="5\\+",replacement="5",x=data)
#[1] "1" "2" "3" "4" "5"
或更一般而言，如果要删除+:
Or more generally, if you want to remove the +:
gsub(pattern="\\+",replacement="",x=data)
如果不转义，+表示前一项将被匹配一次或多次"，因此在您的第二个示例中，"5+"的"5"元素由模式匹配，并由""代替，留下"+".
If unescaped, + means "The preceding item will be matched one or more times", so in your second example, the "5" element of "5+" is matched by the pattern, and replaced by "", leaving you with "+".
这篇关于R:将"+"替换为带gsub的字符的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！