Split one variable into multiple variables in R

Question

I am relatively new to R. My question isn't entirely as straightforward as the title. This is a sample of what df looks like:

id    amenities
1     wireless internet, air conditioning, pool, kitchen
2     pool, kitchen, washer, dryer
3     wireless internet, kitchen, dryer
4     
5     wireless internet

this is what i want df to look like:

id    wireless internet   air conditioning   pool   kitchen   washer   dryer
1     1                   1                  1      1         0        0
2     0                   0                  1      1         1        1
3     1                   0                  0      1         0        1
4     0                   0                  0      0         0        0
5     1                   0                  0      0         0        0

sample code to reproduce data

df <- data.frame(id = c(1, 2, 3, 4, 5),
      amenities = c("wireless internet, air conditioning, pool, kitchen",  
                    "pool, kitchen, washer, dryer", 
                    "wireless internet, kitchen, dryer", 
                    "", 
                    "wireless internet"), 
      stringsAsFactors = FALSE)

Answer 1

FWIW, here's a base R approach (assuming that df contains your data as shown in the question)

dat <- with(df, strsplit(amenities, ', '))
df2 <- data.frame(id = factor(rep(df$id, times = lengths(dat)),
                              levels = df$id),
                  amenities = unlist(dat))
df3 <- as.data.frame(cbind(id = df$id,
                     table(df2$id, df2$amenities)))

This results in

> df3
  id air conditioning dryer kitchen pool washer wireless internet
1  1                1     0       1    1      0                 1
2  2                0     1       1    1      1                 0
3  3                0     1       1    0      0                 1
4  4                0     0       0    0      0                 0
5  5                0     0       0    0      0                 1

Breaking down what is going on:

1. dat <- with(df, strsplit(amenities, ', ')) splits the amenities variable on ', ', resulting in

   > dat
   [[1]]
   [1] "wireless internet" "air conditioning"  "pool"             
   [4] "kitchen"          
   
   [[2]]
   [1] "pool"    "kitchen" "washer"  "dryer"  
   
   [[3]]
   [1] "wireless internet" "kitchen"           "dryer"            
   
   [[4]]
   character(0)
   
   [[5]]
   [1] "wireless internet"
   

2. The second line takes dat and turns it into a vector, and we add on and id column by repeating the origina id values as many times as the number of amenities for that id. This results in

   > df2
      id         amenities
   1   1 wireless internet
   2   1  air conditioning
   3   1              pool
   4   1           kitchen
   5   2              pool
   6   2           kitchen
   7   2            washer
   8   2             dryer
   9   3 wireless internet
   10  3           kitchen
   11  3             dryer
   12  5 wireless internet
   

3. Use the table() function to create the contingency table and then we add on an id column.

Answer 2

A solution using dplyr and tidyr. Notice that I replace "" with None because it is easier to process the column names later.

library(dplyr)
library(tidyr)

df2 <- df %>%
  separate_rows(amenities, sep = ",") %>%
  mutate(amenities = ifelse(amenities %in% "", "None", amenities)) %>%
  mutate(value = 1) %>%
  spread(amenities, value , fill = 0) %>%
  select(-None)
df2
#   id  air conditioning  dryer  kitchen  pool  washer pool wireless internet
# 1  1                 1      0        1     1       0    0                 1
# 2  2                 0      1        1     0       1    1                 0
# 3  3                 0      1        1     0       0    0                 1
# 4  4                 0      0        0     0       0    0                 0
# 5  5                 0      0        0     0       0    0                 1