提取r中分号之间的字符

Question

正在尝试提取分号之间的数据并将该数据放入新列中。

这是一些数据

df <- data.frame(data = c("a;;c;d", "a;b;;d","a;;;d","a;b;;;"), num =c(1:4))

这是我到目前为止从 S.O 中收集到的内容。

res <- df %>% 
  mutate(
    colA = str_extract(data, "^[^;]*(?=;)"),
    colB = str_extract(data, "(?<=;)[^;]*(?=;)"),
    colC = str_extract(data, "(?<=;)(?<=;)[^;]*(?=;)"),
    colD = str_extract(data, "(?<=;)[^;]*$")
  )

它几乎可以满足我的要求，但 colC 与 colB 相同。我不太了解正则表达式，因此非常感谢收到解决方案和解释。

Answer 1

基础 R

cbind(df, read.csv2(text = df$data, header = FALSE))
#     data num V1 V2 V3 V4 V5
# 1 a;;c;d   1  a     c  d NA
# 2 a;b;;d   2  a  b     d NA
# 3  a;;;d   3  a        d NA
# 4 a;b;;;   4  a  b       NA

dplyr

library(dplyr)
df %>%
  mutate(read.csv2(text = data, header = FALSE))
#     data num V1 V2 V3 V4 V5
# 1 a;;c;d   1  a     c  d NA
# 2 a;b;;d   2  a  b     d NA
# 3  a;;;d   3  a        d NA
# 4 a;b;;;   4  a  b       NA

这 没有显式赋值 因为 mutate （和 summarize）会很乐意接受一个命名的-list（其中 data.frame 是一种特殊且兼容的情况。

Answer 2

除了 r2evans 基础 R 和 dplyr：

data.table

library(data.table)

df <- data.table(data = c("a;;c;d", "a;b;;d","a;;;d","a;b;;;"), num =c(1:4))

df[, c("ColA", "ColB", "ColC", "ColD"):=tstrsplit(data, ";")]

df

     data num ColA ColB ColC ColD
1: a;;c;d   1    a         c    d
2: a;b;;d   2    a    b         d
3:  a;;;d   3    a              d
4: a;b;;;   4    a    b

Answer 3

另一个解决方案，使用tidyr::separate：

library(tidyverse)

df <- data.frame(data = c("a;;c;d", "a;b;;d","a;;;d","a;b;;;"), num =c(1:4))

df %>% 
  separate(data, into = str_c("col", letters[1:4]), sep=";", extra="drop")

#>   cola colb colc cold num
#> 1    a         c    d   1
#> 2    a    b         d   2
#> 3    a              d   3
#> 4    a    b             4

提取r中分号之间的字符

Extract characters between semicolons in r

string

split

r

基础 R

dplyr