Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / signal-1.1.3 / dst.m

diff --git a/octave_packages/signal-1.1.3/dst.m b/octave_packages/signal-1.1.3/dst.m
new file mode 100644 (file)
index 0000000..aa82424
--- /dev/null
+++ b/octave_packages/signal-1.1.3/dst.m
@@ -0,0 +1,58 @@
+## Author: Paul Kienzle <pkienzle@users.sf.net> (2006)
+## This program is granted to the public domain.
+
+## -*- texinfo -*-
+## @deftypefn {Function File} {@var{y} =} dst (@var{x})
+## @deftypefnx {Function File} {@var{y} =} dst (@var{x}, @var{n})
+## Computes the type I discrete sine transform of @var{x}.  If @var{n} is given, 
+## then @var{x} is padded or trimmed to length @var{n} before computing the transform.
+## If @var{x} is a matrix, compute the transform along the columns of the
+## the matrix.
+##
+## The discrete sine transform X of x can be defined as follows:
+##
+## @verbatim
+##        N
+## X[k] = sum x[n] sin (pi n k / (N+1) ),  k = 1, ..., N
+##        n=1
+## @end verbatim
+##
+## @seealso{idst}
+## @end deftypefn
+
+function y = dst (x, n)
+
+  if (nargin < 1 || nargin > 2)
+    print_usage;
+  endif
+
+  transpose = (rows (x) == 1);
+  if transpose, x = x (:); endif
+
+  [nr, nc] = size (x);
+  if nargin == 1
+    n = nr;
+  elseif n > nr
+    x = [ x ; zeros(n-nr,nc) ];
+  elseif n < nr
+    x (nr-n+1 : n, :) = [];
+  endif
+
+  y = fft ([ zeros(1,nc); x ; zeros(1,nc); -flipud(x) ])/-2j;
+  y = y(2:nr+1,:);
+  if isreal(x), y = real (y); endif
+
+  ## Compare directly against the slow transform
+  # y2 = x;
+  # w = pi*[1:n]'/(n+1);
+  # for k = 1:n, y2(k) = sum(x(:).*sin(k*w)); end
+  # y = [y,y2];
+
+  if transpose, y = y.'; endif
+
+endfunction
+
+%!test
+%! x = log(linspace(0.1,1,32));
+%! y = dst(x);
+%! assert(y(3), sum(x.*sin(3*pi*[1:32]/33)), 100*eps)