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How to remove duplicate columns from a matrix in R?
To remove duplicate columns from a matrix in R, we can use unique function.
For Example, if we have a matrix called M that contains some duplicate columns then we can use the below command to remove those duplicate columns −
unique(M,MARGIN=2)
Example 1
Following snippet creates a sample matrix −
M1<-matrix(c(rep(10,20),rpois(20,5),rep(10,20)),ncol=3,byrow=FALSE) M1
The following matrix is created −
[,1] [,2] [,3] [1,] 10 3 10 [2,] 10 8 10 [3,] 10 7 10 [4,] 10 6 10 [5,] 10 5 10 [6,] 10 6 10 [7,] 10 2 10 [8,] 10 11 10 [9,] 10 1 10 [10,] 10 2 10 [11,] 10 8 10 [12,] 10 6 10 [13,] 10 6 10 [14,] 10 3 10 [15,] 10 6 10 [16,] 10 2 10 [17,] 10 7 10 [18,] 10 5 10 [19,] 10 7 10 [20,] 10 6 10
To remove duplicate column from matrix M1 on the above created matrix, add the following code to the above snippet −
M1<-matrix(c(rep(10,20),rpois(20,5),rep(10,20)),ncol=3,byrow=FALSE) unique(M1,MARGIN=2)
Output
If you execute all the above given snippets as a single program, it generates the following Output −
[,1] [,2] [1,] 10 3 [2,] 10 8 [3,] 10 7 [4,] 10 6 [5,] 10 5 [6,] 10 6 [7,] 10 2 [8,] 10 11 [9,] 10 1 [10,] 10 2 [11,] 10 8 [12,] 10 6 [13,] 10 6 [14,] 10 3 [15,] 10 6 [16,] 10 2 [17,] 10 7 [18,] 10 5 [19,] 10 7 [20,] 10 6
Example 2
Following snippet creates a sample matrix −
M2<-matrix(c(rpois(20,2),rep(1,20),rpois(20,5),rep(1,20)),ncol=4,byrow=FALSE) M2
The following matrix is created −
[,1] [,2] [,3] [,4] [1,] 1 1 5 1 [2,] 4 1 8 1 [3,] 1 1 6 1 [4,] 1 1 2 1 [5,] 0 1 5 1 [6,] 2 1 5 1 [7,] 3 1 6 1 [8,] 1 1 4 1 [9,] 1 1 7 1 [10,] 0 1 5 1 [11,] 3 1 9 1 [12,] 1 1 2 1 [13,] 1 1 6 1 [14,] 0 1 3 1 [15,] 1 1 2 1 [16,] 0 1 4 1 [17,] 1 1 5 1 [18,] 4 1 3 1 [19,] 3 1 3 1 [20,] 4 1 3 1
To remove duplicate column from matrix M2 on the above created matrix, add the following code to the above snippet −
M2<-matrix(c(rpois(20,2),rep(1,20),rpois(20,5),rep(1,20)),ncol=4,byrow=FALSE) unique(M2,MARGIN=2)
Output
If you execute all the above given snippets as a single program, it generates the following Output −
[,1] [,2] [,3] [1,] 1 1 5 [2,] 4 1 8 [3,] 1 1 6 [4,] 1 1 2 [5,] 0 1 5 [6,] 2 1 5 [7,] 3 1 6 [8,] 1 1 4 [9,] 1 1 7 [10,] 0 1 5 [11,] 3 1 9 [12,] 1 1 2 [13,] 1 1 6 [14,] 0 1 3 [15,] 1 1 2 [16,] 0 1 4 [17,] 1 1 5 [18,] 4 1 3 [19,] 3 1 3 [20,] 4 1 3
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