R Packages stringr - str_match | R包stringr - str_match

 

str_match用法與str_extract用法基本上一樣，差別在於str_extract回傳的是一個list，str_match回傳的是一個陣列

基本語法

str_match(dataset$string, 查找的字元或字串模式)

str_match_all(dataset$string, 查找的字元或字串模式)

有一點要注意一下

• 小寫與大寫判斷為不同字元，需要完全確定大小寫

stringr_df <- tibble(

    weekday = c("Sunday 4", "Monday", "Tuesday", "Wednesday",

    "Thursday 77", "Friday", "Saturday 335")

    )

# 輸出結果

r$> stringr_df # A tibble: 7 x 1 weekday <chr> 1 Sunday 4 2 Monday 3 Tuesday 4 Wednesday 5 Thursday 77 6 Friday 7 Saturday 335

查找數字與全部，查找結果僅以第一個結果位置作為返回條件，若要返回全部數字，需尾端加上" + "，返回時以陣列型式傳回

# 查找數字

str_match(stringr_df$weekday, "\\d")

# 輸出結果

r$> str_match(stringr_df$weekday, "\\d") [,1] [1,] "4" [2,] NA [3,] NA [4,] NA [5,] "7" [6,] NA [7,] "3"

# 查找全部數字

str_match_all(stringr_df$weekday, "\\d")

# 輸出結果

r$> str_match_all(stringr_df$weekday, "\\d") [[1]] [,1] [1,] "4" [[2]] [,1] [[3]] [,1] [[4]] [,1] [[5]] [,1] [1,] "7" [2,] "7" [[6]] [,1] [[7]] [,1] [1,] "3" [2,] "3" [3,] "5"