Generate all posible dummies according values of var in r

Question

I have a dataframe like this:

df <- data.frame(V1=c("a,b,c,d,e,f","a,b,c","e,f","b,d","a,e"))

I want to generate all possible dummies according to categories in var V1, something like this:

df$a <- c(1,1,0,0,1)
df$b <- c(1,1,0,1,0)
df$c <- c(1,1,0,0,0)
df$d <- c(1,0,0,1,0)
df$e <- c(1,0,1,0,1)
df$f <- c(1,0,1,0,0)

> df
           V1 a b c d e f
1 a,b,c,d,e,f 1 1 1 1 1 1
2       a,b,c 1 1 1 0 0 0
3         e,f 0 0 0 0 1 1
4         b,d 0 1 0 1 0 0
5         a,e 1 0 0 0 1 0

How can I do this efficiently? I have a big dataframe and V1 has a lot of categories.

Uwe · Accepted Answer · 2018-06-09T07:40:02.873

Here is a solution which uses strsplit() to split up the character strings and dcast() to reshape from long to wide format:

library(data.table)
setDT(df)[, rn := .I][
  , strsplit(as.character(V1), ","), by = rn][
    , dcast(.SD, rn ~ V1, length)]

   rn a b c d e f
1:  1 1 1 1 1 1 1
2:  2 1 1 1 0 0 0
3:  3 0 0 0 0 1 1
4:  4 0 1 0 1 0 0
5:  5 1 0 0 0 1 0

If V1 is to be included, it can be joined afterwards:

library(data.table) # version 1.11.4 used
setDT(df)[, rn := .I][
  , strsplit(as.character(V1), ","), by = rn][
    , dcast(.SD, rn ~ V1, length)][
      df, on = "rn"][
        , setcolorder(.SD, "V1")]

            V1 rn a b c d e f
1: a,b,c,d,e,f  1 1 1 1 1 1 1
2:       a,b,c  2 1 1 1 0 0 0
3:         e,f  3 0 0 0 0 1 1
4:         b,d  4 0 1 0 1 0 0
5:         a,e  5 1 0 0 0 1 0

setcolorder() is used to move the V1 column to the front.

MKR · Answer 2 · 2018-06-09T08:07:55.950

An option is to use splitstackshape::cSplit to split V1 column. Make sure to use drop = FALSE so that V1 column is retained. Now, convert to long format using tidyr::gather and then reshape2::dcast will convert data in wide format.

library(tidyverse)
library(splitstackshape)
library(reshape2)

df %>% cSplit("V1", drop = FALSE, type.convert = FALSE) %>%
  gather(key, value, -V1) %>%
  filter(!is.na(value)) %>%
  dcast(V1~value, fun.aggregate = length)

#            V1 a b c d e f
# 1       a,b,c 1 1 1 0 0 0
# 2 a,b,c,d,e,f 1 1 1 1 1 1
# 3         a,e 1 0 0 0 1 0
# 4         b,d 0 1 0 1 0 0
# 5         e,f 0 0 0 0 1 1

Data:

df <- data.frame(V1=c("a,b,c,d,e,f","a,b,c","e,f","b,d","a,e"), stringsAsFactors = FALSE)

Generate all posible dummies according values of var in r

2 Answers2