function y = saxpy ( n, sa, x, incx, y, incy )

%% SAXPY adds a constant times one vector to another.
%
%  Modified:
%
%    05 May 2006
%
%  Author:
%
%    MATLAB translation by John Burkardt
%
%  Reference:
%
%    Jack Dongarra, Cleve Moler, Jim Bunch and Pete Stewart,
%    LINPACK User's Guide,
%    SIAM, (Society for Industrial and Applied Mathematics),
%    3600 University City Science Center,
%    Philadelphia, PA, 19104-2688.
%    ISBN 0-89871-172-X
%
%    Charles Lawson, Richard Hanson, David Kincaid, Fred Krogh,
%    Basic Linear Algebra Subprograms for Fortran Usage,
%    Algorithm 539,
%    ACM Transactions on Mathematical Software,
%    Volume 5, Number 3, September 1979, pages 308-323.
%
%  Parameters:
%
%    Input, integer N, the number of entries in the vector.
%
%    Input, real SA, the multiplier.
%
%    Input, real X(*), the vector to be scaled and added to Y.
%
%    Input, integer INCX, the increment between successive entries of X.
%
%    Input/output, real Y(*), the vector to which a 
%    multiple of X is to be added.
%
%    Input, integer INCY, the increment between successive entries of Y.
%
  if ( n <= 0 )

    y = [];

  elseif ( sa == 0.0 )

    
  elseif ( incx == 1 & incy == 1 )

    y(1:n) = y(1:n) + sa * x(1:n);

  else

    if ( 0 <= incx )
      ix = 1;
    else
      ix = ( - n + 1 ) * incx + 1;
    end

    if ( 0 <= incy )
      iy = 1;
    else
      iy = ( - n + 1 ) * incy + 1;
    end

    for i = 1 : n
      y(iy) = y(iy) + sa * x(ix);
      ix = ix + incx;
      iy = iy + incy;
    end

  end