r - 如何替换字符串中某个位置的某个字符？

Question

我有一个问题是如何替换某个位置的字符。例如:

str <- c("abcdccc","hijklccc","abcuioccc")
#I want to replace character "c" which is in position 3 to "X" how can I do that?
#I know the function gsub and substr, but the only idea I have got so far is 
#use if() to make it. How can I do it quickly?
#ideal result
>str
"abXdccc" "hijklccc" "abXuioccc"

Answer 1

这有点尴尬，但是您可以根据单个字符的值替换单个字符，例如:

ifelse(substr(str,3,3)=="c", `substr<-`(str,3,3,"X"), str)
#[1] "abXdccc"   "hijklccc"  "abXuioccc"

如果您愿意覆盖该值，则可以将其做得更简洁:

substr(str[substr(str,3,3)=="c"],3,3) <- "X"
str
#[1] "abXdccc"   "hijklccc"  "abXuioccc"