nonzeros

Use nonzeros to return the nonzero elements in a sparse matrix.

Create a 10-by-10 sparse matrix that contains a few nonzero elements. The typical display of sparse matrices shows a list of the nonzero values and their locations.

A = sparse([1 3 2 1],[1 1 2 3],1:4,10,10)

A = 10x10 sparse double matrix (4 nonzeros)
   (1,1)        1
   (3,1)        2
   (2,2)        3
   (1,3)        4

Find the values of the nonzero elements.

v = nonzeros(A)

v = 4×1

     1
     2
     3
     4

Use nonzeros, nnz, and find to locate and count nonzero matrix elements.

Create a 10-by-10 random sparse matrix with 7% density of nonzeros.

A = sprand(10,10,0.07);

Use nonzeros to find the values of the nonzero elements.

v = nonzeros(A)

v = 7×1

    0.9595
    0.4218
    0.7922
    0.8003
    0.1419
    0.9157
    0.6557

Use nnz to count the number of nonzeros.

n = nnz(A)

n = 
7

Use find to get the indices and values of the nonzeros.

[i,j,v] = find(A)

i = 7×1

    10
     3
     9
     1
     2
     7
    10

j = 7×1

     2
     5
     6
    10
    10
    10
    10

v = 7×1

    0.9595
    0.4218
    0.7922
    0.8003
    0.1419
    0.9157
    0.6557