function [A,xy,B,hbtype,rhstype] = hbo(file)%HBO	Read and process a Harwell-Boeing sparse matrix file.%	A = HBO('matfile') gets the sparse matrix from the specified .mat file.%%	[A,xy,B,hbtype,rhstype] = HBO('matfile') also gets:%       xy: node coordinates (if present)%       B:  right-hand sides, starting guesses, or exact solutions (if present)%       hbtype: matrix type, which will be one of the following three-letter%	        codes: CSA, PRA, PSA, PSE, PUA, RRA, RSA, RUA, RZA, UNK%       rhstype: a description of B, for which see the user's guide.%%	In addition to reading the file, HBO assembles any unassembled matrices,%	symmetrizes any symmetric matrices, and implicitizes any explicit zeros.%%	HBO .mat files are created from Harwell-Boeing data files by the%	stand-alone Fortran process, HBO2MAT.  These .mat files contain:%%	    For assembled, type xxA, matrices:%	        A       - the sparse matrix.%	        hbtitle - The first 72 characters of the first "card".%	        hbname  - The matrix name, same as file name without .mat.%	        hbtype  - One of those three letter codes.%	        hbfill  - If present, the value inserted in pattern matrices.%	        hbzero  - If present, the value inserted for explicit zeros.%	        rhstype - If present, the right hand side type.%               xy      - If present, a matrix whose rows are node coordinates.%               B       - If present, a matrix whose columns are right-hand%                         sides, etc.%%	    For unassembled, xxE, matrices:%	        hbtitle - The first 72 characters of the first "card".%	        hbname  - The matrix name, same as file name without .mat.%	        hbtype  - Only type PSE exists in current collection.%	        varind and elptr - The indices specifying the locations%	            of the constituent elements.%%  Say "help harwell" for more information about the collection.%  See also HBOLIST, HBOFIND.%	Cleve Moler, The MathWorks, 4/2/94.load(file)if ~exist('hbtype')   hbtype = 'UNK';   A = A;% PSE  - Pattern symmetric unassembledelseif strcmp(hbtype,'PSE')   n1 = length(elptr);   elptr(n1) = [];   J = varind;   I = zeros(size(J));   I(elptr) = ones(size(elptr));   I = cumsum(I);   A = sparse(I,J,1);   A = A'*A;% RSA  - Real symmetricelseif strcmp(hbtype,'RSA')   A = A + A' - diag(diag(A));% RZA  - Real skew symmetricelseif strcmp(hbtype,'RZA')   A = A - A';% RUA  - Real unsymmetricelseif strcmp(hbtype,'RUA')   A = A;% RRA  - Real rectangularelseif strcmp(hbtype,'RRA')   A = A;% CSA  - Complex symmetricelseif strcmp(hbtype,'CSA')   A = A + A' - diag(diag(A));% PSA  - Pattern symmetricelseif strcmp(hbtype,'PSA')   A = A + A' - diag(diag(A));% PUA  - Pattern unsymmetricelseif strcmp(hbtype,'PUA')   A = A;% PRA  - Pattern rectangularelseif strcmp(hbtype,'PRA')   A = A;else   error(['Harwell-Boeing type ' hbtype ' unexpected.'])end% Remove any explict zerosif exist('hbzero')   k = find(A == hbzero);   A(k) = sparse(length(k),1);end% Get any right-hand side vectors or coordinates.if exist('xyz')    xy = xyz;end;if ~exist('xy')    xy = [];end;if ~exist('B')    B = [];    rhstype = 'NON';end;if ~exist('rhstype')    rhstype = 'UNK';end;