Sparse Matirx

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David Chen
David Chen 2011-11-21
编辑： John D'Errico 2018-3-17
How to code sparse matrix from the existing matrix?

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回答（2 个）

Andrei Bobrov
Andrei Bobrov 2011-11-21
A = rand(10)
A(A>.15) = 0 % existing matrix
Asp = sparse(A) % sparse matrix
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KAKOLI DEY
KAKOLI DEY 2018-3-17
if I take temperature data matrix how would i convert yhis into a sparse

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John D'Errico
John D'Errico 2018-3-17
编辑：John D'Errico 2018-3-17
From what existing matrix? In what form?
If you already have a matrix, then the sparse function will convert it to sparse form. Thus
A = rand(6);
A(A > .1) = 0;
A here is a FULL matrix, even though it is mostly zero.
A
A =
0 0 0 0 0 0
0 0.084436 0 0 0 0
0 0 0 0 0.075967 0.049654
0.0046342 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
As you can see, A is full, just a double precision matrix.
whos A
Name Size Bytes Class Attributes
A 6x6 288 double
A is convertible into sparse form, trivially, using sparse.
As = sparse(A)
As =
(4,1) 0.0046342
(2,2) 0.084436
(3,5) 0.075967
(3,6) 0.049654
whos As
Name Size Bytes Class Attributes
As 6x6 120 double sparse
If you have a matrix in some other form, perhaps a list of row and column indices and values, then again, sparse does the job.
Or, perhaps you have the matrix in the form of known diagonals. Then spdiags is the proper tool.
But we cannot read your mind as to what you have. Just telling us that you have a "temperature data matrix" is nothing of value. It is insufficient information.

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