Plots the sparsity pattern of a sparse matrix. The syntax for its use is
spy(x)
which uses a default color and symbol. Alternately, you can use
spy(x,colspec)
where colspec
is any valid color and symbol spec accepted by plot
.
First, an example of a random sparse matrix.
--> y = sprand(1000,1000,.001) y = <double> - size: [999 1000] Matrix is sparse with 999 nonzeros --> spy(y,'ro')
which is shown here
Here is a sparse matrix with a little more structure. First we build a
sparse matrix with block diagonal structure, and then use spy
to
visualize the structure.
--> A = sparse(1000,1000); --> for i=1:25; A((1:40) + 40*(i-1),(1:40) + 40*(i-1)) = 1; end; --> spy(A,'gx') --> hold on --> y = sprand(A); --> spy(y,'ro');
with the result shown here