Question

我想提取[和,之间的值，并将这些提取的值放在新列（col2）中。

我不反对使用stringr代替基地。

示例数据：

df <- structure(list(t = structure(1:2, .Label = c("v1", "v2"), class = "factor"), 
    d = structure(1:2, .Label = c("something[123,894]", "something[456,4834]"
    ), class = "factor")), .Names = c("t", "d"), row.names = c(NA, 
-2L), class = "data.frame")

看起来像：

   t                   d
1 v1  something[123,894]
2 v2 something[456,4834]

现在，我想制作一个新列（df$r）并将123和v1的值456提取为v2 {{1} }}

我确信有一种简单的方法可以使用正则表达式搜索df$r和[来执行此操作，但我使用,并不是很好。

感谢您的帮助。

-cherrytree

Answer 1

df <- structure(list(t = structure(1:2, .Label = c("v1", "v2"), class = "factor"), 
                     d = structure(1:2, .Label = c("something[123,894]", "something[456,4834]"
                     ), class = "factor")), .Names = c("t", "d"), row.names = c(NA, 
                                                                                -2L), class = "data.frame")

这将匹配任意字符.*和[，然后捕获到组\\1一个或多个数字\\d+，结束捕获组，然后任何次数的任何字符

df$r <- gsub('.*\\[(\\d+).*', '\\1', df$d)

#    t                   d   r
# 1 v1  something[123,894] 123
# 2 v2 something[456,4834] 456

另外，如果你想在逗号后面捕获第二个数字串，这会更有用：

gsub('.*\\[(\\d+),(\\d+).*', '\\1', df$d)
# [1] "123" "456"
gsub('.*\\[(\\d+),(\\d+).*', '\\2', df$d)
# [1] "894"  "4834"

或者，如果你想一气呵成：

cbind(df, do.call('rbind', lapply(strsplit(as.character(df$d), ','),
                                  function(x) gsub('\\D', '', x))))

#    t                   d   1    2
# 1 v1  something[123,894] 123  894
# 2 v2 something[456,4834] 456 4834

This解释得比我好：

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))
--------------------------------------------------------------------------------
  \[                       '['
--------------------------------------------------------------------------------
  (                        group and capture to \1:
--------------------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )                        end of \1
--------------------------------------------------------------------------------
  ,                        ','
--------------------------------------------------------------------------------
  (                        group and capture to \2:
--------------------------------------------------------------------------------
    \d+                      digits (0-9) (1 or more times (matching
                             the most amount possible))
--------------------------------------------------------------------------------
  )                        end of \2
--------------------------------------------------------------------------------
  .*                       any character except \n (0 or more times
                           (matching the most amount possible))

使用R在特殊字符之间提取值

1 个答案: