SJSU Singular Matrix Database

## SJget MATLAB interface to the SJSU Singular Matrix Collection:

The SJget interface provides
for access to the collection from inside your MATLAB workspace.
From inside MATLAB, SJget will download a matrix, cache it locally, and
load it into your MATLAB workspace. You don't need to use a browser to get a matrix.
For example to download the 10th matrix from the SJSU Singular site, from
inside Matlab:
Prob = SJget(10); % Prob is a struct (matrix, name, meta-data, ...)
A = Prob.A ; % A is a numerically singular matrix
svals = Prob.svals; % the singular values of A
SJplot(Prob),shg % plot the singular value spectrum of A
disp( SJrank(Prob) ) % display the numerical rank of the matrix

You can also search for matrices that fit your
criteria and reorder the matrices -- from inside MATLAB. For example, to download all
symmetric matrices
into MATLAB, and order them in increasing numerical rank:
index = SJget ; % get index of the SJSU Singular Matrix Collection
ids = find (index.numerical_symmetry == 1) ;
[ignore, i] = sort (index.numrank (ids)) ;
ids = ids (i) ;
for id = ids
Prob = SJget (id); % Prob is a struct (matrix, name, meta-data, ...)
A = Prob.A ; % A is a symmetric matrix
disp([SJrank(Prob),size(A)]) % list the numerical rank and size of A
end

To install SJget download the appropriate compressed file below. Move, from inside
Matlab 7.0 or later, to the folder containing the unzipped files and type SJget_install.

SJget is derivative work and is based on UFget from
SuiteSparse by
Timothy Davis (however code from
SuiteSparse is
not needed to use SJget). Our discussion of the use of SJget is similar to the
discussion of UFget at
The University
of Florida Sparse Matrix Collection.