[英]Using gsub for a specific occurrence in a string in R?
I have two strings:我有两个字符串:
mystring1 <- c("hello i am a cat. just kidding, i'm not a cat i'm a cat. dogs are the best animal. not cats!")
mystring2 <- c("hello i am a cat. just kidding, i'm not a cat i'm a cat. but i have a cat friend that is a cat.")
I want to change the third occurrence of the word cat in both strings to dog.我想将两个字符串中单词 cat 的第三次出现更改为 dog。
Ideally, string1
and string2
would read:理想情况下,
string1
和string2
将读取:
mystring1
[1] "hello i am a cat. just kidding, i'm not a cat i'm a dog. dogs are the best animal. not cats!"
mystring2
[1] "hello i am a cat. just kidding, i'm not a cat i'm a dog. but i have a cat friend that is a cat."
What is the best way of doing this?这样做的最佳方法是什么? Up until now I have only used
gsub
to replace characters but I don't know if this can be used to replace specific occurrences of a character.到目前为止,我只使用
gsub
替换字符,但我不知道这是否可以用来替换特定出现的字符。
You could use你可以使用
mystring1 <- c("hello i am a cat. just kidding, i'm not a cat i'm a cat. dogs are the best animal. not cats!")
mystring2 <- c("hello i am a cat. just kidding, i'm not a cat i'm a cat. but i have a cat friend that is a cat who knows a cat knowing a cat.")
sub("((cat.*?){2})\\bcat\\b", "\\1dog", mystring1, perl=TRUE)
which gives这使
> sub("((cat.*?){2})\\bcat\\b", "\\1dog", c(mystring1, mystring2), perl=TRUE)
[1] "hello i am a cat. just kidding, i'm not a cat i'm a dog. dogs are the best animal. not cats!"
[2] "hello i am a cat. just kidding, i'm not a cat i'm a dog. but i have a cat friend that is a cat who knows a cat knowing a cat."
You can use gsubfn
您可以使用
gsubfn
library(gsubfn)
p <- proto(fun = function(this, x) if(count == 3) 'dog' else x)
gsubfn('cat', p, c(mystring1, mystring2))
# [1] "hello i am a cat. just kidding, i'm not a cat i'm a dog. dogs are the best animal. not cats!"
# [2] "hello i am a cat. just kidding, i'm not a cat i'm a dog. but i have a cat friend that is a cat."
Or, if it needs to be surrounded by word boundaries,或者,如果它需要被单词边界包围,
gsubfn('\\bcat\\b', p, c(mystring1, mystring2), perl = TRUE)
# [1] "hello i am a cat. just kidding, i'm not a cat i'm a dog. dogs are the best animal. not cats!"
# [2] "hello i am a cat. just kidding, i'm not a cat i'm a dog. but i have a cat friend that is a cat."
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