Create column based on unique values

Question

I'd like to create columns in a data frame based on the unique values from a single column.

E.g.

Column1
A
B
C

Into

A     B      C
True  False  False
False True   False
False False  True

Answer 1

We can use table

!!table(1:nrow(df1), df1$Column1)
#       A     B     C
#  1  TRUE FALSE FALSE
#  2 FALSE  TRUE FALSE
#  3 FALSE FALSE  TRUE

---

Or using mtabulate from qdapTools

library(qdapTools)
mtabulate(df1$Column1)!=0
#         A     B     C
#[1,]  TRUE FALSE FALSE
#[2,] FALSE  TRUE FALSE
#[3,] FALSE FALSE  TRUE

---

Or using model.matrix

 model.matrix(~Column1-1, df1)!=0
 #  Column1A Column1B Column1C
 #1     TRUE    FALSE    FALSE
 #2    FALSE     TRUE    FALSE
 #3    FALSE    FALSE     TRUE

Answer 2

You could also use a loop,

sapply(df$Column1, function(i) grepl(i, df$Column1))
#         A     B     C
#[1,]  TRUE FALSE FALSE
#[2,] FALSE  TRUE FALSE
#[3,] FALSE FALSE  TRUE

Answer 3

You can also use dcast from reshape2 package

library(reshape2)
!is.na(dcast(df, Column1 ~ Column1))[, -1]

#       A     B     C
#[1,]  TRUE FALSE FALSE
#[2,] FALSE  TRUE FALSE
#[3,] FALSE FALSE  TRUE