1######################################################################## 2## 3## Copyright (C) 2004-2021 The Octave Project Developers 4## 5## See the file COPYRIGHT.md in the top-level directory of this 6## distribution or <https://octave.org/copyright/>. 7## 8## This file is part of Octave. 9## 10## Octave is free software: you can redistribute it and/or modify it 11## under the terms of the GNU General Public License as published by 12## the Free Software Foundation, either version 3 of the License, or 13## (at your option) any later version. 14## 15## Octave is distributed in the hope that it will be useful, but 16## WITHOUT ANY WARRANTY; without even the implied warranty of 17## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18## GNU General Public License for more details. 19## 20## You should have received a copy of the GNU General Public License 21## along with Octave; see the file COPYING. If not, see 22## <https://www.gnu.org/licenses/>. 23## 24######################################################################## 25 26## -*- texinfo -*- 27## @deftypefn {} {@var{s} =} speye (@var{m}, @var{n}) 28## @deftypefnx {} {@var{s} =} speye (@var{m}) 29## @deftypefnx {} {@var{s} =} speye (@var{sz}) 30## Return a sparse identity matrix of size @var{m}x@var{n}. 31## 32## The implementation is significantly more efficient than 33## @code{sparse (eye (@var{m}))} as the full matrix is not constructed. 34## 35## Called with a single argument a square matrix of size 36## @var{m}-by-@var{m} is created. If called with a single vector argument 37## @var{sz}, this argument is taken to be the size of the matrix to create. 38## @seealso{sparse, spdiags, eye} 39## @end deftypefn 40 41function s = speye (m, n) 42 43 if (nargin == 1) 44 if (isvector (m) && length (m) == 2) 45 n = m(2); 46 m = m(1); 47 elseif (isscalar (m)) 48 n = m; 49 else 50 error ("speye: invalid matrix dimension"); 51 endif 52 else 53 if (! isscalar (m) || ! isscalar (n)) 54 error ("speye: invalid matrix dimension"); 55 endif 56 endif 57 58 lo = min ([m, n]); 59 s = sparse (1:lo, 1:lo, 1, m, n); 60 61endfunction 62 63 64%!assert (issparse (speye (4))) 65%!assert (speye (4), sparse (1:4,1:4,1)) 66%!assert (speye (2,4), sparse (1:2,1:2,1,2,4)) 67%!assert (speye (4,2), sparse (1:2,1:2,1,4,2)) 68%!assert (speye ([4,2]), sparse (1:2,1:2,1,4,2)) 69