Map vector to key-value list using purrr:map

user_6326148 0
Viewed 482

I want to map a vector to the key-value list. I would like to get a list using purrr:map (or other tidyverse method) where keys would be the characters before the first comma and values (vectors) the rest of characters. My solution using a for loop: 

v <- c("a,1,2", "b,4,5,6", "c,x")
l <- list()

for(vv in v) {
  vv_split <- vv %>% stringr::str_split(",")
  l[[vv_split[[1]][1]]] <- vv_split[[1]][-1]
}
purrr vector r list
2 Answers

Here is one option with read.csv and split

df1 <- read.csv(text = v, header = FALSE, stringsAsFactors = FALSE)
lapply(split(df1[-1], df1[,1]), function(x) na.omit(unlist(x, use.names = FALSE)))

Or another option with tidyverse

library(dplyr)
library(tibble)
library(tidyr)
enframe(v) %>%
     separate_rows(value) %>% 
     group_by(name) %>% 
     mutate(name1 = value[1]) %>%
     slice(-1) %>%
     ungroup %>% 
     select(-name) %>% 
     unstack(value ~ name1)
#$a
#[1] "1" "2"

#$b
#[1] "4" "5" "6"

#$c
#[1] "x"

Or with str_remove and str_replace

str_remove(v, '.,') %>% 
      strsplit(',') %>% 
      set_names(str_extract(v, '.'))
#$a
#[1] "1" "2"

#$b
#[1] "4" "5" "6"

#$c
#[1] "x"
user_37322710

I think a bit simpler solution is

library(tidyverse)
v <- c("a,1,2", "b,4,5,6", "c,x")

# Split each string into its character elements
l <- str_split(v, ",") %>% 
  # Extract the first element to use as the list element name
  set_names(., map(., 1)) %>% 
  # Remove the first element
  map(tail, -1)
l
# > $a
# > [1] "1" "2"
# > 
# > $b
# > [1] "4" "5" "6"
# > 
# > $c
# > [1] "x"

Though the set_names step could use some improvement in readability.

user_29305960
Related