使用 R 将大小不等的字符串列拆分为多列

Question

There is a string column like this, in my data frame.

str=as.character(c("M 12; M 13","M 24", NA, "C 12; C 50; C 78"))
no=seq(1:4)
data.frame(no,str)

  no              str
1  1       M 12; M 13
2  2             M 24
3  3             <NA>
4  4 C 12; C 50; C 78

It has multiple values, separated by ";"symbol. I need to split this into multiple columns (3 columns based on this example) as each column contains only one value of the string. Will this be possible using R?

Answer 1

This is a good occasion to make use of extra = merge argument of separate :

library(dplyr)
df %>% 
  separate(str, c('A', 'B', 'C'), sep= ";", extra = 'merge')

  no    A     B     C
1  1 M 12  M 13  <NA>
2  2 M 24  <NA>  <NA>
3  3 <NA>  <NA>  <NA>
4  4 C 12  C 50  C 78

Answer 2

You can use str_split :

library(tidyverse)

df <- data.frame(str = c("M 12; M 13","M 24", NA, "C 12; C 50; C 78"),
                 no = seq(1:4))

df %>%
  mutate(splits = str_split(str, "; ")) %>%
  unnest_wider(splits)

which gives:

# A tibble: 4 x 5
  str                 no ...1  ...2  ...3 
  <chr>            <int> <chr> <chr> <chr>
1 M 12; M 13           1 M 12  M 13  <NA> 
2 M 24                 2 M 24  <NA>  <NA> 
3 <NA>                 3 <NA>  <NA>  <NA> 
4 C 12; C 50; C 78     4 C 12  C 50  C 78