tidyr 的 extract

R 中级正则表达式

Angelo Zehr

Data Journalist

目前用到的函数

• str_match
• str_replace
• str_match_all
• str_replace_all
• …

当正则表达式遇上数据框：

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

extract 的参数

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

• data

• col

• into

• regex

• remove

• convert

Movies 数据框

str_match 能做什么

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

str_match 的结果是什么样

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

str_match 只能匹配一条信息

extract 能为我们做什么

extract 能为我们做什么

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

extract 的结果

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

开始练习吧！

R 中级正则表达式