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How to combine two rows in R matrix by addition?
To combine two rows in R matrix by addition, we can follow the below steps −
First of all, create a matrix.
Then, using plus sign (+) to add two rows and store the addition in one of the rows.
After that, remove the row that is not required by subsetting with single square brackets.
Example
Create the matrix
Let’s create a matrix as shown below −
M<-matrix(sample(1:5,100,replace=TRUE),ncol=4) M
Output
On executing, the above script generates the below output(this output will vary on your system due to randomization) −
[,1] [,2] [,3] [,4] [1,] 4 4 2 1 [2,] 5 4 4 4 [3,] 1 1 5 3 [4,] 1 4 4 4 [5,] 5 1 1 3 [6,] 3 1 2 1 [7,] 4 4 5 2 [8,] 3 4 2 1 [9,] 2 2 4 4 [10,] 4 1 1 2 [11,] 5 3 1 2 [12,] 3 1 2 4 [13,] 3 3 2 3 [14,] 3 3 1 1 [15,] 5 5 5 5 [16,] 4 1 2 5 [17,] 4 2 5 1 [18,] 3 4 1 5 [19,] 5 3 4 4 [20,] 2 5 1 1 [21,] 5 3 5 5 [22,] 2 4 2 3 [23,] 5 5 2 5 [24,] 3 5 4 1 [25,] 4 1 2 5
Add two rows
Using plus sign to add row 1 and row 2 then storing the sum in row 1 −
M<-matrix(sample(1:5,100,replace=TRUE),ncol=4) M[1,]<-M[1,]+M[2,] M
Output
[,1] [,2] [,3] [,4] [1,] 9 8 6 5 [2,] 5 4 4 4 [3,] 1 1 5 3 [4,] 1 4 4 4 [5,] 5 1 1 3 [6,] 3 1 2 1 [7,] 4 4 5 2 [8,] 3 4 2 1 [9,] 2 2 4 4 [10,] 4 1 1 2 [11,] 5 3 1 2 [12,] 3 1 2 4 [13,] 3 3 2 3 [14,] 3 3 1 1 [15,] 5 5 5 5 [16,] 4 1 2 5 [17,] 4 2 5 1 [18,] 3 4 1 5 [19,] 5 3 4 4 [20,] 2 5 1 1 [21,] 5 3 5 5 [22,] 2 4 2 3 [23,] 5 5 2 5 [24,] 3 5 4 1 [25,] 4 1 2 5
Remove the row which is not required
Using single square subsetting to remove 2nd row from matrix M −
M<-matrix(sample(1:5,100,replace=TRUE),ncol=4) M[1,]<-M[1,]+M[2,] M[-2,]
Output
[,1] [,2] [,3] [,4] [1,] 9 8 6 5 [2,] 1 1 5 3 [3,] 1 4 4 4 [4,] 5 1 1 3 [5,] 3 1 2 1 [6,] 4 4 5 2 [7,] 3 4 2 1 [8,] 2 2 4 4 [9,] 4 1 1 2 [10,] 5 3 1 2 [11,] 3 1 2 4 [12,] 3 3 2 3 [13,] 3 3 1 1 [14,] 5 5 5 5 [15,] 4 1 2 5 [16,] 4 2 5 1 [17,] 3 4 1 5 [18,] 5 3 4 4 [19,] 2 5 1 1 [20,] 5 3 5 5 [21,] 2 4 2 3 [22,] 5 5 2 5 [23,] 3 5 4 1 [24,] 4 1 2 5
Updated on: 08-Nov-2021
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