Matlab code for Permuted LU decomposition
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This is a permuted LU decomposition
but its showing error as not enough input arguments
function [P, L, U, sign] = splu(A)
% splu Square PA=LU factorization *with row exchanges*.
%
% [P, L, U] = splu(A), for a square, invertible matrix A,
% uses Gaussian elimination to compute a permutation
% matrix P, a lower triangular matrix L and
% an upper triangular matrix U so that P*A = L*U.
% P, L and U are the same size as A.
% sign = det(P); it is 1 or -1.
%
% See also slu, lu, rref, partic, nulbasis, colbasis.
[m, n] = size(A);
if m ~= n
error('Matrix must be square.')
end
P = eye(n, n);
L = eye(n, n);
U = zeros(n, n);
tol = sqrt(eps);
sign = 1;
for k = 1:n
if abs(A(k, k)) < tol
for r = k:n
if abs(A(r, k)) >= tol
break
end
if r == n
if nargout == 4
sign = 0;
return
else
disp('A is singular within tolerance.')
error(['No pivot in column ' int2str(k) '.'])
end
end
end
A([r k], 1:n) = A([k r], 1:n);
if k > 1, L([r k], 1:k-1) = L([k r], 1:k-1); end
P([r k], 1:n) = P([k r], 1:n);
sign = -sign;
end
for i = k+1:n
L(i, k) = A(i, k) / A(k, k);
for j = k+1:n
A(i, j) = A(i, j) - L(i, k)*A(k, j);
end
end
for j = k:n
U(k, j) = A(k, j) * (abs(A(k, j)) >= tol);
end
end
if nargout < 4
roworder = P*(1:n)';
disp('Pivots in rows:'), disp(roworder'); end
end
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