How to change a matrix into a triple in R language (i.e. three columns: row, col, value)

bing On the search :

How a matrix becomes a triple , stay bing Search results on :

Various C Language , I can't find R The implementation of language .

R The cycle of language writing is very slow , Just use the ready-made bag

Matrix

Matrix Is a very powerful package , It can transform a matrix into a sparse matrix , take 0 Turn into ., Saving resource .

test , Generate 10*10 Matrix , There's a lot of 0, Now it is not 0 The place is transformed into the form of triples .

What is meant by A triple , Even if the matrix is transformed into a three column form , The matrix is two-dimensional , Now extract the line numbers , As the first column , Extract the column number , As the second column , The corresponding values are extracted , As the third column .

such as :

Log in and copy

       

        1 2
        
3 4
       
       

        
1.
        
2.
       

To become a triple is :

Log in and copy

       

        1 1 1
        
1 2 2
        
2 1 3
        
2 2 4
       
       

        
1.
        
2.
        
3.
        
4.
       

Test data

Log in and copy

       

        #  The matrix becomes a triple : R Language  Matrix
        
mm = matrix(sample(c(0,0,2),size = 100,replace = T),10,10)
        
#  Suppose it is a symmetric matrix ,  Keep only the lower triangle ,  So the triangle is 0
        
mm[upper.tri(mm)] = 0
        
mm
       
       

        
1.
        
2.
        
3.
        
4.
        
5.
       

Log in and copy

       

        > mm
        
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
        
 [1,]    2    0    0    0    0    0    0    0    0     0
        
 [2,]    0    2    0    0    0    0    0    0    0     0
        
 [3,]    0    2    2    0    0    0    0    0    0     0
        
 [4,]    0    0    0    0    0    0    0    0    0     0
        
 [5,]    0    0    0    0    2    0    0    0    0     0
        
 [6,]    0    0    0    2    2    0    0    0    0     0
        
 [7,]    0    0    0    0    0    0    0    0    0     0
        
 [8,]    2    0    0    0    2    0    0    0    0     0
        
 [9,]    0    0    0    2    0    2    0    0    0     0
        
[10,]    0    0    0    0    0    0    0    2    2     0
       
       

        
1.
        
2.
        
3.
        
4.
        
5.
        
6.
        
7.
        
8.
        
9.
        
10.
        
11.
        
12.
       

Into a sparse matrix :

You can see , Sparse matrix all 0 Have become a dot .

Log in and copy

       

        library(Matrix)
        
smm = Matrix(mm)
        
smm
       
       

        
1.
        
2.
        
3.
       

Log in and copy

       

        > smm
        
10 x 10 sparse Matrix of class "dtCMatrix"
        

        
 [1,] 2 . . . . . . . . .
        
 [2,] . 2 . . . . . . . .
        
 [3,] . 2 2 . . . . . . .
        
 [4,] . . . . . . . . . .
        
 [5,] . . . . 2 . . . . .
        
 [6,] . . . 2 2 . . . . .
        
 [7,] . . . . . . . . . .
        
 [8,] 2 . . . 2 . . . . .
        
 [9,] . . . 2 . 2 . . . .
        
[10,] . . . . . . . 2 2 .
       
       

        
1.
        
2.
        
3.
        
4.
        
5.
        
6.
        
7.
        
8.
        
9.
        
10.
        
11.
        
12.
        
13.
       

Transform a sparse matrix into a triple

Log in and copy

       

        #  Become triple 
        
re = summary(smm)
        
sm = as.data.frame(re)
        
sm
       
       

        
1.
        
2.
        
3.
        
4.
       

result :

Log in and copy

       

        > sm
        
    i j x
        
1   1 1 2
        
2   8 1 2
        
3   2 2 2
        
4   3 2 2
        
5   3 3 2
        
6   6 4 2
        
7   9 4 2
        
8   5 5 2
        
9   6 5 2
        
10  8 5 2
        
11  9 6 2
        
12 10 8 2
        
13 10 9 2
       
       

        
1.
        
2.
        
3.
        
4.
        
5.
        
6.
        
7.
        
8.
        
9.
        
10.
        
11.
        
12.
        
13.
        
14.
        
15.
       

This should be a more efficient method .

Complete code :

Log in and copy

       

        #  The matrix becomes a triple : R Language  Matrix
        
mm = matrix(sample(c(0,0,2),size = 100,replace = T),10,10)
        
mm
        

        
#  Suppose it is a symmetric matrix ,  Keep only the lower triangle ,  So the triangle is 0
        
mm[upper.tri(mm)] = 0
        
mm
        

        
library(Matrix)
        
smm = Matrix(mm)
        
smm
        

        
#  Become triple 
        
re = summary(smm)
        
sm = as.data.frame(re)
        
sm
        
library(dplyr)
        
arrange(sm,i,j)
       
       

        
1.
        
2.
        
3.
        
4.
        
5.
        
6.
        
7.
        
8.
        
9.
        
10.
        
11.
        
12.
        
13.
        
14.
        
15.
        
16.
        
17.
        
18.