r - 将句子的第一个单词大写(regex、gsub、gregexpr)

Question

假设我有以下文本:

txt <- as.character("this is just a test! i'm not sure if this is O.K. or if it will work? who knows. regex is sorta new to me..  There are certain cases that I may not figure out??  sad!  ^_^")

我想将句子的第一个字母字符大写。

我想出了要匹配的正则表达式:^|[[:alnum:]]+[[:alnum:]]+[.!?]+[[:space:]]*[[ :space:]]+[[:alnum:]]

调用 gregexpr 返回:

> gregexpr("^|[[:alnum:]]+[[:alnum:]]+[.!?]+[[:space:]]*[[:space:]]+[[:alnum:]]", txt)
[[1]]
[1]   1  16  65  75 104 156
attr(,"match.length")
[1] 0 7 7 8 7 8
attr(,"useBytes")
[1] TRUE

哪些是匹配的正确子串索引。

但是，我该如何实现才能正确地将我需要的字符大写？我假设我必须 strsplit 然后...？

Answer 1

看来你的regex 对你的例子不起作用，所以我从this question 偷了一个.

txt <- as.character("this is just a test! i'm not sure if this is O.K. or if it will work? who knows. regex is sorta new to me..  There are certain cases that I may not figure out??  sad!  ^_^")
print(txt)

gsub("([^.!?\\s])([^.!?]*(?:[.!?](?!['\"]?\\s|$)[^.!?]*)*[.!?]?['\"]?)(?=\\s|$)", "\\U\\1\\E\\2", txt, perl=T, useBytes = F)