idamnjanovic@1: function Y = spdiag(V,K)
idamnjanovic@1: %SPDIAG Sparse diagonal matrices.
idamnjanovic@1: %   SPDIAG(V,K) when V is a vector with N components is a sparse square
idamnjanovic@1: %   matrix of order N+ABS(K) with the elements of V on the K-th diagonal. 
idamnjanovic@1: %   K = 0 is the main diagonal, K > 0 is above the main diagonal and K < 0
idamnjanovic@1: %   is below the main diagonal. 
idamnjanovic@1: %
idamnjanovic@1: %   SPDIAG(V) is the same as SPDIAG(V,0) and puts V on the main diagonal.
idamnjanovic@1: %
idamnjanovic@1: %   See also DIAG, SPDIAGS.
idamnjanovic@1: 
idamnjanovic@1: 
idamnjanovic@1: %  Ron Rubinstein
idamnjanovic@1: %  Computer Science Department
idamnjanovic@1: %  Technion, Haifa 32000 Israel
idamnjanovic@1: %  ronrubin@cs
idamnjanovic@1: %
idamnjanovic@1: %  June 2008
idamnjanovic@1: 
idamnjanovic@1: 
idamnjanovic@1: if (nargin<2)
idamnjanovic@1:   K = 0;
idamnjanovic@1: end
idamnjanovic@1: 
idamnjanovic@1: n = length(V) + abs(K);
idamnjanovic@1: 
idamnjanovic@1: if (K>0)
idamnjanovic@1:   i = 1:length(V);
idamnjanovic@1:   j = K+1:n;
idamnjanovic@1: elseif (K<0)
idamnjanovic@1:   i = -K+1:n;
idamnjanovic@1:   j = 1:length(V);
idamnjanovic@1: else
idamnjanovic@1:   i = 1:n;
idamnjanovic@1:   j = 1:n;
idamnjanovic@1: end
idamnjanovic@1: 
idamnjanovic@1: Y = sparse(i,j,V(:),n,n);