Fill a matrix with another matrix in R

Question

I want to fill the matrix with other matrix, is the below code correct?

pivot_simplex_fract<-function(matrice){

  n_row_matrix_2<-nrow(matrix_Standard) #number of the matrix

  n_col_matrix_2<-ncol(matrix_Standard)

  for (i in n_row_matrix_2){

    for (j in n_col_matrix_2) {

      matrix<-fractions(matrice[i,j])

    }

  }

  return(matrix)

}

Answer 1

See basically you are using the fractions function that has derived from the MASS packages which can work with matrices. But you don't really need to have a double loop. Let us say that you have a matrix as such:

X <- diag(5)/5

X

     [,1] [,2] [,3] [,4] [,5]

[1,]  0.2  0.0  0.0  0.0  0.0

[2,]  0.0  0.2  0.0  0.0  0.0

[3,]  0.0  0.0  0.2  0.0  0.0

[4,]  0.0  0.0  0.0  0.2  0.0

[5,]  0.0  0.0  0.0  0.0  0.2

You can also subset the rows and columns easily by the following code:

fractions(X)[1:3, 1:3]

     [,1] [,2] [,3]

[1,] 1/5    0    0 

[2,]   0  1/5    0 

[3,]   0    0  1/5

If you are a beginner ad want to know more about R the do check out the following R programming tutorial.