Matlab sparse matrix does not come out as I would expect

12 vues (au cours des 30 derniers jours)
Zeyuan
Zeyuan le 3 Fév 2025
Commenté : Zeyuan le 3 Fév 2025
This is my code:
S=sparse([1 3 2 1 4],[3 1 4 1 4],[1 2 3 4 5],4,4)
full(s)
However, when I run it, I get:
'S =
(1,1) 4
(3,1) 2
(1,3) 1
(2,4) 3
(4,4) 5
ans=
0 0 0 1
0 1 0 0
1 2 0 0
0 0 3 0'
Please tell me why ans is not [4 0 1 0;0 0 0 3; 2 0 0 0; 0 0 0 5]?

Réponse acceptée

John D'Errico
John D'Errico le 3 Fév 2025
Modifié(e) : John D'Errico le 3 Fév 2025
S=sparse([1 3 2 1 4],[3 1 4 1 4],[1 2 3 4 5],4,4)
S = 4x4 sparse double matrix (5 nonzeros)
(1,1) 4 (3,1) 2 (1,3) 1 (2,4) 3 (4,4) 5
full(S)
ans = 4×4
4 0 1 0 0 0 0 3 2 0 0 0 0 0 0 5
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It works just fine.
What did you do wrong? LOOK CAREFULLY AT WHAT YOU WROTE. MATLAB is case sensitive in variable names.
You created the matrix S. Then you looked at full(s). Should MATLAB know that you wanted to see what was in the variable S, and not in the variable s? The mind reading toolbox never works correctly. ;-)

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