tidyr 的 extract

R 中級 Regular Expressions

Angelo Zehr

Data Journalist

目前用到的函式

• str_match
• str_replace
• str_match_all
• str_replace_all
• ...

規則表示式與資料框交會點：

extract(
    data,
    col,
    into,
    regex = "([[:alnum:]]+)",
    remove = TRUE,
    convert = FALSE,
    ...
 )

extract 的引數

extract(
    data,
    col,
    into,
    regex = "([[:alnum:]]+)",
    remove = TRUE,
    convert = FALSE,
    ...
 )

• data

• col

• into

• regex

• remove

• convert

Movies 資料框

str_match 能做到的事

screens_per_movie %<>%
  mutate(
    is_3d = str_match(line, "3D")
  )

str_match 的結果長怎樣

screens_per_movie %<>%
  mutate(
    is_3d = str_match(line, "3D")
  )

str_match 只能擷取一項資訊

extract 能幫上的忙

extract 能幫上的忙

extract(
  screens_per_movie,
  col = "line",
  into = c("is_3d", "screens"),
  regex = "(3D).*?(\\d+)$",
  remove = FALSE
 )

extract 的結果

extract(
  screens_per_movie,
  col = "line",
  into = c("is_3d", "screens"),
  regex = "(3D).*?(\\d+)$",
  remove = FALSE
)

一起來練習吧！

R 中級 Regular Expressions