MATLAB Mathematics - SERC - Index of
MATLAB Mathematics - SERC - Index of MATLAB Mathematics - SERC - Index of
6 Sparse Matrices west0479 west0479 = (25,1) 1.0000e+00 (31,1) -3.7648e-02 (87,1) -3.4424e-01 (26,2) 1.0000e+00 (31,2) -2.4523e-02 (88,2) -3.7371e-01 (27,3) 1.0000e+00 (31,3) -3.6613e-02 (89,3) -8.3694e-01 (28,4) 1.3000e+02 . . . nonzeros(west0479); ans = 1.0000e+00 -3.7648e-02 -3.4424e-01 1.0000e+00 -2.4523e-02 -3.7371e-01 1.0000e+00 -3.6613e-02 -8.3694e-01 1.3000e+02 . . . Note Use Ctrl+C to stop the nonzeros listing at any time. 6-14
Viewing Sparse Matrices Note that initially nnz has the same value as nzmax by default. That is, the number of nonzero elements is equivalent to the number of storage locations allocated for nonzeros. However, MATLAB does not dynamically release memory if you zero out additional array elements. Changing the value of some matrix elements to zero changes the value of nnz, but not that of nzmax. However, you can add as many nonzero elements to the matrix as desired. You are not constrained by the original value of nzmax. Viewing Sparse Matrices Graphically It is often useful to use a graphical format to view the distribution of the nonzero elements within a sparse matrix. The MATLAB spy function produces a template view of the sparsity structure, where each point on the graph represents the location of a nonzero array element. For example, spy(west0479) 0 50 100 150 200 250 300 350 400 450 0 100 200 300 400 nz = 1887 6-15
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- Page 242 and 243: 6 Sparse Matrices Function Summary
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- Page 248 and 249: 6 Sparse Matrices S = (3,1) 1 (2,2)
- Page 250 and 251: 6 Sparse Matrices Now F = full(S) d
- Page 252 and 253: 6 Sparse Matrices Importing Sparse
- Page 256 and 257: 6 Sparse Matrices The find Function
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- Page 268 and 269: 6 Sparse Matrices Similarly, S(:,p)
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6 Sparse Matrices<br />
west0479<br />
west0479 =<br />
(25,1) 1.0000e+00<br />
(31,1) -3.7648e-02<br />
(87,1) -3.4424e-01<br />
(26,2) 1.0000e+00<br />
(31,2) -2.4523e-02<br />
(88,2) -3.7371e-01<br />
(27,3) 1.0000e+00<br />
(31,3) -3.6613e-02<br />
(89,3) -8.3694e-01<br />
(28,4) 1.3000e+02<br />
.<br />
.<br />
.<br />
nonzeros(west0479);<br />
ans =<br />
1.0000e+00<br />
-3.7648e-02<br />
-3.4424e-01<br />
1.0000e+00<br />
-2.4523e-02<br />
-3.7371e-01<br />
1.0000e+00<br />
-3.6613e-02<br />
-8.3694e-01<br />
1.3000e+02<br />
.<br />
.<br />
.<br />
Note Use Ctrl+C to stop the nonzeros listing at any time.<br />
6-14