convert dummy data frame into data frame

Question

I have a dummy data frame of dimension 8x12, and I want to group the variables x1j in x1, x2j in x2 and x3j in x3. Creating a data frame of 8x4 dimension.

set.seed(123)
df <- data.frame(replicate(4,as.factor(sample(1:3,8,rep=TRUE))))

library(dummies)
df.dummy <- dummy.data.frame(df)

My dummy data frame

df.dummy
  X11 X12 X13 X21 X22 X23 X31 X32 X33 X41 X42 X43
1   1   0   0   0   1   0   1   0   0   0   1   0
2   0   0   1   0   1   0   1   0   0   0   0   1
3   0   1   0   0   0   1   1   0   0   0   1   0
4   0   0   1   0   1   0   0   0   1   0   1   0
5   0   0   1   0   0   1   0   0   1   1   0   0
6   1   0   0   0   1   0   0   0   1   1   0   0
7   0   1   0   1   0   0   0   1   0   0   0   1
8   0   0   1   0   0   1   0   0   1   0   0   1

Expected output

df
  X1 X2 X3 X4
1  1  2  1  2
2  3  2  1  3
3  2  3  1  2
4  3  2  3  2
5  3  3  3  1
6  1  2  3  1
7  2  1  2  3
8  3  3  3  3

If I have a data frame, in which the columns are of the type factors, can I create a dummy data frame, with the function dummy.data.frame (), is there any function that does the inverse? From dummy to grouped data.frame.

score 6 · Accepted Answer · answered Sep 01 '18 at 19:15

df.dummy <- structure(list(X11 = c(1L, 0L, 0L, 0L, 0L, 1L, 0L, 0L), X12 = c(0L, 
0L, 1L, 0L, 0L, 0L, 1L, 0L), X13 = c(0L, 1L, 0L, 1L, 1L, 0L, 
0L, 1L), X21 = c(0L, 0L, 0L, 0L, 0L, 0L, 1L, 0L), X22 = c(1L, 
1L, 0L, 1L, 0L, 1L, 0L, 0L), X23 = c(0L, 0L, 1L, 0L, 1L, 0L, 
0L, 1L), X31 = c(1L, 1L, 1L, 0L, 0L, 0L, 0L, 0L), X32 = c(0L, 
0L, 0L, 0L, 0L, 0L, 1L, 0L), X33 = c(0L, 0L, 0L, 1L, 1L, 1L, 
0L, 1L), X41 = c(0L, 0L, 0L, 0L, 1L, 1L, 0L, 0L), X42 = c(1L, 
0L, 1L, 1L, 0L, 0L, 0L, 0L), X43 = c(0L, 1L, 0L, 0L, 0L, 0L, 
1L, 1L)), .Names = c("X11", "X12", "X13", "X21", "X22", "X23", 
"X31", "X32", "X33", "X41", "X42", "X43"), class = "data.frame",
row.names =  c("1", "2", "3", "4", "5", "6", "7", "8"))

ASSIGN <- gl(4, 3)  ## 4 factor variable; each 3 levels
as.data.frame(lapply(split.default(df.dummy, ASSIGN), max.col))
#  X1 X2 X3 X4
#1  1  2  1  2
#2  3  2  1  3
#3  2  3  1  2
#4  3  2  3  2
#5  3  3  3  1
#6  1  2  3  1
#7  2  1  2  3
#8  3  3  3  3

There are other ways to generate the ASSIGN. Basically it tells how to group columns of df.dummy into the right factor variable.

convert dummy data frame into data frame

1 Answers1