> text <- c("we are the world", "we are the children")
> sub("w", "W", text)
[1] "We are the world" "We are the children"
> sub("W","w",text)
[1] "we are the world" "we are the children"
> gsub("W","w",text)
[1] "we are the world" "we are the children"
> gsub("w","W",text)
[1] "We are the World" "We are the children"
> sub(" ", "", "abc def ghi")
[1] "abcdef ghi"
> ## [1] "abcdef ghi"
> gsub(" ", "", "abc def ghi")
[1] "abcdefghi"
> ## [1] "abcdefghi"
從上面的輸出結果可以看出，sub（）和gsub（）的區別在於，前者只替換第一次匹配的字符串，而后者會替換掉所有匹配的字符串。
從上面的輸出結果可以看出，sub()和gsub()的區別在於，前者只替換第一次匹配的字串（請注意輸出結果中world的首字母），而后者會替換掉所有匹配的字串。
注意：gsub()是對向量里面的每個元素進行搜素，如果發現元素里面有多個位置匹配了模式，則全部進行替換，而grep()也是對向量里每個元素進行搜索，但它僅僅知道元素是否匹配了模式（並返回該元素在向量中的下標），但具體元素中匹配了多少次卻無法知道。在這里僅僅是為了說明這兩者的區別，這在實際中可能不會用到。