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How to extract diagonal elements of a matrix in R without using diag function?
The diagonal elements of a matrix occur at the position where column and row indices are same hence, we can make use of those indices to extract diagonal elements of a matrix if we do not want to use diag function.
For example, if we have a matrix called M then diagonal elements of M can be extracted by using the command given below −
M[row(M)==col(M)]
Check out the below examples to understand how it works.
Example 1
Following snippet creates a matrix −
M1<-matrix(rpois(25,1),ncol=5) M1
The following matrix is created −
[,1][,2][,3][,4][,5] [1,] 0 1 1 2 0 [2,] 1 0 0 1 1 [3,] 1 0 0 0 3 [4,] 0 0 1 1 1 [5,] 2 1 1 1 1
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M1<-matrix(rpois(25,1),ncol=5) M1[row(M1)==col(M1)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 0 0 0 1 1
Example 2
Following snippet creates a matrix −
M2<-matrix(rpois(25,2),ncol=5) M2
The following matrix is created −
[,1][,2][,3][,4][,5] [1,] 2 3 2 3 3 [2,] 1 4 3 3 2 [3,] 3 3 1 3 3 [4,] 1 0 4 2 1 [5,] 0 1 2 0 0
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M2<-matrix(rpois(25,2),ncol=5) M2[row(M2)==col(M2)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 2 4 1 2 0
Example 3
Following snippet creates a matrix −
M3<-matrix(rpois(25,10),ncol=5) M3
The following matrix is created −
[,1][,2][,3][,4][,5] [1,] 7 10 13 8 3 [2,] 5 9 9 8 7 [3,] 12 7 15 6 9 [4,] 15 8 10 11 16 [5,] 8 10 16 10 7
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M3<-matrix(rpois(25,10),ncol=5) M3[row(M3)==col(M3)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 7 9 15 11 7
Example 4
Following snippet creates a matrix −
M4<-matrix(rpois(25,50),ncol=5) M4
The following matrix is created −
[,1][,2][,3][,4][,5] [1,] 48 40 42 44 53 [2,] 46 47 56 43 41 [3,] 47 54 53 40 50 [4,] 39 50 53 55 48 [5,] 57 57 43 57 64
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M4<-matrix(rpois(25,50),ncol=5) M4[row(M4)==col(M4)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 48 47 53 55 64
Example 5
Following snippet creates a matrix −
M5<-matrix(rpois(25,500),ncol=5) M5
The following matrix is created −
[,1][,2][,3][,4][,5] [1,] 501 506 543 506 518 [2,] 466 531 530 496 505 [3,] 510 497 516 522 505 [4,] 455 521 504 476 493 [5,] 465 520 490 501 476
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M5<-matrix(rpois(25,500),ncol=5) M5[row(M5)==col(M5)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 501 531 516 476 476
Example 6
Following snippet creates a matrix −
M6<-matrix(round(rnorm(25),1),ncol=5) M6
The following matrix is created −
[,1] [,2] [,3] [,4] [,5] [1,] -2.1 1.0 0.3 1.4 -1.2 [2,] -0.1 0.1 -0.2 -1.1 0.7 [3,] -1.6 -0.6 -0.2 1.5 -1.0 [4,] -0.7 1.2 -1.5 -0.9 0.1 [5,] 1.2 0.5 1.8 -0.6 0.4
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M6<-matrix(round(rnorm(25),1),ncol=5) M6[row(M6)==col(M6)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] -2.1 0.1 -0.2 -0.9 0.4
Example 7
Following snippet creates a matrix −
M7<-matrix(round(runif(25,2,5),2),ncol=5) M7
The following matrix is created −
[,1] [,2] [,3] [,4] [,5] [1,] 4.63 3.45 2.22 4.31 3.46 [2,] 2.22 3.65 3.15 4.19 2.65 [3,] 3.14 3.68 2.31 3.04 3.45 [4,] 3.71 4.91 3.94 2.55 2.98 [5,] 3.48 2.54 2.29 3.58 3.15
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M7<-matrix(round(runif(25,2,5),2),ncol=5) M7[row(M7)==col(M7)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 4.63 3.65 2.31 2.55 3.15
Example 8
Following snippet creates a matrix −
M8<-matrix(round(rexp(25,2.05),2),ncol=5) M8
The following matrix is created −
[,1] [,2] [,3] [,4] [,5] [1,] 0.60 0.15 0.32 0.42 0.16 [2,] 0.59 0.40 0.95 0.23 1.07 [3,] 0.02 0.57 0.79 0.21 0.09 [4,] 1.03 0.25 0.25 1.08 0.46 [5,] 0.10 0.68 0.13 0.47 0.01
To extract diagonal elements of a matrix in R without using diag function, add the following code to the above snippet −
M8<-matrix(round(rexp(25,2.05),2),ncol=5) M8[row(M8)==col(M8)]
Output
If you execute all the above given snippets as a single program, it generates the following output −
[1] 0.60 0.40 0.79 1.08 0.01
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