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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function d=%sp_diag(a,k)
// %sp_diag - implement diag function for sparse matrix, rational matrix ,..
[lhs,rhs]=argn(0)
if rhs==1 then k=0,end
[ij,v,sz]=spget(a)
m=sz(1);n=sz(2)
if m>1&n>1 then
l=find(ij(:,1)==(ij(:,2)-k))
if k<=0 then
mn=min(m+k,n)
i0=-k
else
mn=min(m,n-k)
i0=0
end
kk=abs(k)
if l==[] then d=sparse([],[],[mn,1]);return;end
d=sparse([ij(l,1)-i0,ones(ij(l,1))],v(l),[mn,1])
else
if m>1 then ij=ij(:,1);else ij=ij(:,2);end
nn = max(m,n)+abs(k)
if ij==[] then
d=sparse([],[],[nn,nn])
else
if k>0 then
d=sparse([ij,ij+k],v,[nn,nn])
else
d=sparse([ij-k,ij],v,[nn,nn])
end
end
end
endfunction
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