Add Column in R Data Frame

Since no one is perfect, people might forget to add all columns that are necessary for the analysis but this problem can be solved. If a column is missing in our data frame and we came to know about it later then it can be added easily with the help of reordering the columns.

Example

Consider the below data frame −

> x1<-1:20
> x2<-letters[1:20]
> x3<-rep(c(1,2),times=10)
> df<-data.frame(x1,x2,x3)
> df
   x1 x2 x3
1   1 a 1
2   2 b 2
3   3 c 1
4   4 d 2
5   5 e 1
6   6 f 2
7   7 g 1
8   8 h 2
9   9 i 1
10 10 j 2
11 11 k 1
12 12 l 2
13 13 m 1
14 14 n 2
15 15 o 1
16 16 p 2
17 17 q 1
18 18 r 2
19 19 s 1
20 20 t 2

Let’s say a column y1 is missing that needs to be in between x1 and x2 then it can be created and added as shown below −

> df$y1<-rep(c(22,24,26,28),times=5)
> df<-df[,c("x1","y1","x2","x3")]
> df
   x1 y1 x2 x3
1   1 22  a  1
2   2 24  b  2
3   3 26  c  1
4   4 28  d  2
5   5 22  e  1
6   6 24  f  2
7   7 26  g  1
8   8 28  h  2
9   9 22  i  1
10 10 24  j  2
11 11 26  k  1
12 12 28  l  2
13 13 22  m  1
14 14 24  n  2
15 15 26  o  1
16 16 28  p  2
17 17 22  q  1
18 18 24  r  2
19 19 26  s  1
20 20 28  t  2

Suppose another column is missing which should be in the last position then it can be created and added as follows −

> df$y2<-rep(c(100,105,110,115,120),times=4)
> df<-df[,c("x1","y1","x2","x3","y2")]
> df
   x1 y1  x2  x3  y2
1   1 22  a  1  100
2   2 24  b  2  105
3   3 26  c  1  110
4   4 28  d  2  115
5   5 22  e  1  120
6   6 24  f  2  100
7   7 26  g  1  105
8   8 28  h  2  110
9   9 22  i  1  115
10 10 24  j  2  120
11 11 26  k  1  100
12 12 28  l  2  105
13 13 22  m  1  110
14 14 24  n  2  115
15 15 26  o  1  120
16 16 28  p  2  100
17 17 22  q  1  105
18 18 24  r  2  110
19 19 26  s  1  115
20 20 28  t  2  120