How to set the diagonal elements of a matrix to 1 in R?
First thing we need to understand is diagonal elements are useful only if we have a square matrix, otherwise it would not make sense to set diagonal elements, this is known to almost all mathematicians but some freshman might get confused because we can create diagonal in a non-square matrix which should not be called a diagonal. In R, we can set the diagonal elements of a matrix to 1 by using diag function.
Example1
Live Demo
> M1<-matrix(1:25,ncol=5)
> M1
Output
[,1] [,2] [,3] [,4] [,5]
[1,] 1 6 11 16 21
[2,] 2 7 12 17 22
[3,] 3 8 13 18 23
[4,] 4 9 14 19 24
[5,] 5 10 15 20 25
> diag(M1)<-1
> M1
Output
[,1] [,2] [,3] [,4] [,5]
[1,] 1 6 11 16 21
[2,] 2 1 12 17 22
[3,] 3 8 1 18 23
[4,] 4 9 14 1 24
[5,] 5 10 15 20 1
Example2
Live Demo
> M2<-matrix(rpois(36,5),ncol=6)
> M2
Output
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 5 4 4 5 6 5
[2,] 4 5 7 8 3 4
[3,] 4 3 6 5 5 6
[4,] 7 4 4 6 2 6
[5,] 2 5 2 4 6 6
[6,] 7 2 3 5 4 3
> diag(M2)<-1
> M2
Output
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 4 4 5 6 5
[2,] 4 1 7 8 3 4
[3,] 4 3 1 5 5 6
[4,] 7 4 4 1 2 6
[5,] 2 5 2 4 1 6
[6,] 7 2 3 5 4 1
Example3
Live Demo
> M3<-matrix(rpois(64,10),ncol=8)
> M3
Output
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,] 8 9 17 7 12 11 4 10
[2,] 8 15 8 7 13 10 13 11
[3,] 13 9 9 13 4 10 11 9
[4,] 9 9 7 10 5 13 11 5
[5,] 7 9 9 8 9 11 8 15
[6,] 12 8 10 14 15 3 4 8
[7,] 9 8 7 11 11 11 10 6
[8,] 7 12 6 11 10 6 9 7
> diag(M3)<-1
> M3
Output
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8]
[1,] 1 9 17 7 12 11 4 10
[2,] 8 1 8 7 13 10 13 11
[3,] 13 9 1 13 4 10 11 9
[4,] 9 9 7 1 5 13 11 5
[5,] 7 9 9 8 1 11 8 15
[6,] 12 8 10 14 15 1 4 8
[7,] 9 8 7 11 11 11 1 6
[8,] 7 12 6 11 10 6 9 1
Example4
Live Demo
> M4<-matrix(sample(1:10,100,replace=TRUE),ncol=10)
> M4
Output
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 4 8 8 1 8 6 1 4 10 7
[2,] 4 8 3 4 8 5 10 3 10 9
[3,] 8 2 1 7 4 7 7 9 3 5
[4,] 6 2 9 2 10 2 2 2 6 4
[5,] 6 9 4 8 2 1 8 4 7 7
[6,] 2 9 7 9 1 6 10 8 7 9
[7,] 3 6 2 7 5 2 7 3 1 5
[8,] 1 6 6 10 2 7 6 2 1 9
[9,] 1 1 6 3 10 1 4 4 9 3
[10,] 7 10 3 7 10 10 4 10 1 9
> diag(M4)<-1
> M4
Output
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 1 8 8 1 8 6 1 4 10 7
[2,] 4 1 3 4 8 5 10 3 10 9
[3,] 8 2 1 7 4 7 7 9 3 5
[4,] 6 2 9 1 10 2 2 2 6 4
[5,] 6 9 4 8 1 1 8 4 7 7
[6,] 2 9 7 9 1 1 10 8 7 9
[7,] 3 6 2 7 5 2 1 3 1 5
[8,] 1 6 6 10 2 7 6 1 1 9
[9,] 1 1 6 3 10 1 4 4 1 3
[10,] 7 10 3 7 10 10 4 10 1 1
Example5
Live Demo
> M5<-matrix(sample(0:9,25,replace=TRUE),ncol=5)
> M5
Output
[,1] [,2] [,3] [,4] [,5]
[1,] 6 6 9 9 0
[2,] 2 4 3 9 7
[3,] 1 7 8 3 8
[4,] 9 5 0 4 6
[5,] 9 7 0 1 3
> diag(M5)<-1
> M5
Output
[,1] [,2] [,3] [,4] [,5]
[1,] 1 6 9 9 0
[2,] 2 1 3 9 7
[3,] 1 7 1 3 8
[4,] 9 5 0 1 6
[5,] 9 7 0 1 1
Published on 06-Nov-2020 15:19:54
