function A = banded (m, n, k, l)
%
% A = banded (m, n, k, l)
%
% generate a band matrix with both upper bandwidth k and lower bandwidth l.  
% k=1 and l=1 means a tridiagonal matrix.  if k is not present, k=1, l=1.

%   Copyright 2009, Sivasankaran Rajamanickam, Timothy A. Davis
%   http://www.cise.ufl.edu/research/sparse

if (nargin < 3)
    k = 1 ;
end
if (nargin < 4)
    l = k ;
end
if (nargin < 1)
    m = 30 ;
    n = 30 ;
end

A1 = randn(m, n) ;
A = triu (tril(A1, k), -l) ;
A = sparse(A) ;