function b=dst(a,n)
%DST    Discrete sine transform.
%
%       Y = DST(X) returns the discrete sine transform of X.
%       The vector Y is the same size as X and contains the
%       discrete sine transform coefficients.
%
%       Y = DST(X,N) pads or truncates the vector X to length N
%       before transforming.
%
%       If X is a matrix, the DST operation is applied to each
%       column. This transform can be inverted using IDST.
%
%       See also: FFT, IFFT, IDST.

%       A. Nordmark 10-25-94.
%       Copyright (c) 1994-98 by The MathWorks, Inc.
%       $Revision: 1.7 $  $Date: 1997/11/25 17:04:56 $


error(nargchk(1,2,nargin));

if min(size(a))==1
    if size(a,2)>1
        do_trans = 1;
    else
        do_trans = 0;
    end
    a = a(:);
else
    do_trans = 0;
end
if nargin==1,
  n = size(a,1);
end
m = size(a,2);

% Pad or truncate a if necessary
if size(a,1)<n,
  aa = zeros(n,m);
  aa(1:size(a,1),:) = a;
else
  aa = a(1:n,:);
end

y=zeros(2*(n+1),m);
y(2:n+1,:)=aa;
y(n+3:2*(n+1),:)=-flipud(aa);
yy=fft(y);
b=yy(2:n+1,:)/(-2*sqrt(-1));

if isreal(a), b = real(b); end
if do_trans, b = b.'; end

