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# How to find the row that has maximum number of duplicates in an R matrix?

To find the row that has maximum number of duplicates in an R matrix, we can follow the below steps −

- First of all, create a matrix.
- Then, convert matrix into data.table then use order function with head function to find the row that has maximum number of duplicates.

## Create the matrix

Let’s create a matrix as shown below −

M<-matrix(rpois(40,1),ncol=2) M

On executing, the above script generates the below output(this output will vary on your system due to randomization) −

[,1] [,2] [1,] 2 2 [2,] 0 1 [3,] 2 2 [4,] 1 0 [5,] 1 2 [6,] 3 0 [7,] 1 0 [8,] 0 0 [9,] 0 3 [10,] 0 1 [11,] 1 0 [12,] 1 0 [13,] 1 1 [14,] 0 1 [15,] 1 2 [16,] 0 0 [17,] 1 0 [18,] 1 1 [19,] 2 2 [20,] 1 2

## Find the row that has maximum number of duplicates

Loading data.table package then converting matrix M into data.table object and finding the row that has maximum number of duplicates −

M<-matrix(rpois(40,1),ncol=2) library(data.table) DT<-data.table(M) head(DT[,list(Duplicates=.N),by=names(DT)][order(Duplicates,decreasing=T)],1)

### Output

V1 V2 Duplicates 1: 1 0 5

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