How to add a column between columns or after last column in an 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