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How to find the number of columns where all row values are equal in R matrix?
To find the number of columns where all row values are equal in R matrix, we can follow the below steps −
First of all, create a matrix.
Then, use sum function along with length and apply function to find the number of columns where all row values are equal.
Example 1
Create the matrix
Let’s create a matrix as shown below −
M1<-matrix(rpois(50,5),ncol=2) M1
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
[,1] [,2] [1,] 10 3 [2,] 5 7 [3,] 4 5 [4,] 3 8 [5,] 8 4 [6,] 3 6 [7,] 4 3 [8,] 4 4 [9,] 4 4 [10,] 5 6 [11,] 4 2 [12,] 2 3 [13,] 3 3 [14,] 4 3 [15,] 5 5 [16,] 5 7 [17,] 5 1 [18,] 4 5 [19,] 2 3 [20,] 5 2 [21,] 7 3 [22,] 6 6 [23,] 6 2 [24,] 3 2 [25,] 0 6
Find the number of columns where all row values are equal
Using sum function along with length and apply function to find the number of columns where all row values are equal in matrix M1 −
M1<-matrix(rpois(50,5),ncol=2) sum(apply(M1, 1, function(x) length(unique(x))==1))
Output
[1] 7
Example 2
Create the matrix
Let’s create a matrix as shown below −
M2<-matrix(sample(1:5,50,replace=TRUE),ncol=2) M2
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
[,1] [,2] [1,] 3 4 [2,] 4 1 [3,] 4 3 [4,] 1 2 [5,] 2 1 [6,] 1 4 [7,] 1 3 [8,] 3 4 [9,] 3 1 [10,] 2 5 [11,] 2 2 [12,] 1 1 [13,] 3 1 [14,] 1 5 [15,] 3 3 [16,] 3 4 [17,] 3 4 [18,] 4 4 [19,] 2 5 [20,] 4 4 [21,] 2 5 [22,] 5 2 [23,] 4 4 [24,] 4 5 [25,] 2 3
Find the number of columns where all row values are equal
Using sum function along with length and apply function to find the number of columns where all row values are equal in matrix M2 −
M2<-matrix(sample(1:5,50,replace=TRUE),ncol=2) sum(apply(M2, 1, function(x) length(unique(x))==1))
Output
[1] 6
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