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## -*- texinfo -*-
## @deftypefn {} {@var{x} =} spconvert (@var{m})
## Convert a simple sparse matrix format easily generated by other programs
## into Octave's internal sparse format.
##
## The input @var{m} is either a 3 or 4 column real matrix, containing the
## row, column, real, and imaginary parts of the elements of the sparse
## matrix.  An element with a zero real and imaginary part can be used to
## force a particular matrix size.
## @seealso{sparse}
## @end deftypefn

function s = spconvert (m)

  if (nargin < 1)
    print_usage ();
  endif

  if (issparse (m))
    s = m;
  else
    sz = size (m);
    if (! ismatrix (m) || ! isreal (m)
        || length (sz) != 2 || (sz(2) != 3 && sz(2) != 4))
      error (["spconvert: argument must be sparse or real matrix" ...
              "with 3 or 4 columns"]);
    elseif (sz(2) == 3)
      s = sparse (m(:,1), m(:,2), m(:,3));
    else
      s = sparse (m(:,1), m(:,2), m(:,3) + 1i*m(:,4));
    endif
  endif

endfunction


%!test
%! i = [1; 3; 5];
%! j = [2; 4; 6];
%! v = [7; 8; 9];
%! s = spconvert ([i, j, v]);
%! assert (issparse (s));
%! [fi, fj, fv] = find (s);
%! assert (isequal (i, fi) && isequal (j, fj) && isequal (v, fv));
%! s = spconvert ([i, j, v, j]);
%! [fi, fj, fv] = find (s);
%! assert (isequal (i, fi) && isequal (j, fj) && isequal (complex (v, j), fv));
%! assert (size (spconvert ([1, 1, 3; 5, 15, 0])), [5, 15]);

## Test input validation
%!error <Invalid call> spconvert ()
%!error spconvert ({[1 2 3]})
%!error spconvert ([1 2])
%!error spconvert ([1 2 3i])
%!error spconvert ([1 2 3 4 5])