--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/scripts/plot/__quiver__.m	Mon Nov 26 20:42:11 2007 +0000
@@ -0,0 +1,222 @@
+## Copyright (C) 2007 David Bateman
+##
+## This file is part of Octave.
+##
+## Octave is free software; you can redistribute it and/or modify it
+## under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 3 of the License, or (at
+## your option) any later version.
+##
+## Octave is distributed in the hope that it will be useful, but
+## WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+## General Public License for more details.
+##
+## You should have received a copy of the GNU General Public License
+## along with Octave; see the file COPYING.  If not, see
+## <http://www.gnu.org/licenses/>.
+
+## Undocumented internal function
+
+function hlist = __quiver__ (varargin)
+  h = varargin {1};
+  is3d = varargin {2};
+
+  s = 1;
+  arrowsize = 0.33;
+
+  firstnonnumeric = Inf;
+  for i = 3:nargin
+    if (! isnumeric (varargin {i}))
+      firstnonnumeric = i;
+      break;
+    endif
+  endfor
+
+  ioff = 3;
+  if (nargin < (6 + is3d) || firstnonnumeric < (6 + is3d))
+    u = varargin{ioff++};
+    v = varargin{ioff++};
+    if (is3d)
+      w = varargin{ioff++}
+      [x, y, z] = meshgrid (1:size(u,1), 1:size(u,2), 1:max(size(w)));
+    else
+      [x, y] = meshgrid (1:size(u,1), 1:size(u,2));
+    endif
+    if (nargin >= ioff && isnumeric (varargin{ioff}) && 
+	isscalar (varargin{ioff}))
+      s = varargin{ioff++};
+    endif
+  else
+    x = varargin{ioff++};
+    y = varargin{ioff++};
+    if (is3d)
+      z = varargin{ioff++};
+    endif
+    u = varargin{ioff++};
+    v = varargin{ioff++}; 
+    if (is3d)
+      w = varargin{ioff++};
+      if (isvector(x) && isvector(y) && isvector(z) && 
+	  (!isvector (u) || !isvector (v) || !isvector(w)))
+	[x, y, z] = meshgrid (x, y, z);
+      endif
+    else
+      if (isvector(x) && isvector(y) && (!isvector (u) || !isvector (v)))
+	[x, y] = meshgrid (x, y);
+      endif
+    endif
+    if (nargin >= ioff && isnumeric (varargin{ioff}) && 
+	isscalar (varargin{ioff}))
+      s = varargin{ioff++};
+    endif
+  endif
+
+  have_filled = false;
+  have_line_spec = false;
+  while (ioff <= nargin)
+    arg = varargin {ioff++};
+    if (ischar (arg) && strncmp (tolower (arg), "filled", 6))
+      have_filled = true;
+    elseif ((isstr (arg) || iscell (arg))
+	    && ! have_line_spec)
+      [linespec, valid] = __pltopt__ ("quiver", arg, false);
+      if (valid)
+	have_line_spec = true;
+	if (strncmp (linespec.linestyle, "none", 4))
+	  linespec.linestyle = "-";
+	endif
+      else
+	error ("quiver: invalid linespec");
+      endif
+    else
+      error ("quiver: unrecognized argument");
+    endif
+  endwhile
+
+  if (s)
+    ## Scale the arrows to fit in the grid
+    dx = (max(x(:)) - min(x(:))) ./ size (x, 2);
+    dy = (max(y(:)) - min(y(:))) ./ size (y, 1);
+    if (is3d)
+      ## What should this be divided by? The below seems right
+      dz = (max(z(:)) - min(z(:))) ./ max (size (z));
+      len = max (sqrt (u(:).^2 + dy(:).^2) + dz(:).^2);
+    else
+      len = max (sqrt (u(:).^2 + dy(:).^2));
+      dz = 0;
+    endif
+    if (len > 0)
+      s = s / sqrt (2) * sqrt (dx.^2 + dy.^2 + dz.^2) / len; 
+      u = s * u;
+      v = s * v;
+      if (is3d)
+	w = s*w;
+      endif
+    endif
+  endif
+
+  x = x(:);
+  y = y(:);
+  xend = x + u(:);
+  yend = y + v(:);
+  if (is3d)
+    z = z(:);
+    zend = z + w(:);
+  endif
+
+  hstate = get (h, "nextplot");
+  unwind_protect
+    if (have_line_spec)
+      if (is3d)
+	h1 = plot3 ([x.'; xend.'; NaN(1, length (x))](:),
+		    [y.'; yend.'; NaN(1, length (y))](:),
+		    [z.'; zend.'; NaN(1, length (z))](:),
+		    "linestyle", linespec.linestyle);
+      else
+	h1 = plot ([x.'; xend.'; NaN(1, length (x))](:),
+		   [y.'; yend.'; NaN(1, length (y))](:),
+		   "linestyle", linespec.linestyle);
+      endif
+    else
+      if (is3d)
+	h1 = plot3 ([x.'; xend.'; NaN(1, length (x))](:),
+		    [y.'; yend.'; NaN(1, length (y))](:),
+		    [z.'; zend.'; NaN(1, length (z))](:));
+      else
+	h1 = plot ([x.'; xend.'; NaN(1, length (x))](:),
+		   [y.'; yend.'; NaN(1, length (y))](:));
+      endif
+    endif
+    hold on;
+
+    xtmp = x + u(:) .* (1 - arrowsize);
+    ytmp = y + v(:) .* (1 - arrowsize);
+    xarrw1 = xtmp + (y - yend) * arrowsize / 3;
+    xarrw2 = xtmp - (y - yend) * arrowsize / 3;
+    yarrw1 = ytmp - (x - xend) * arrowsize / 3;
+    yarrw2 = ytmp + (x - xend) * arrowsize / 3;
+    if (is3d)
+      zarrw1 = zarrw2 = zend - w(:) * arrowsize / 3;
+    endif
+
+    if (have_line_spec)
+      if (isfield (linespec, "marker") && 
+	! strncmp (linespec.marker, "none", 4))
+	if (is3d)
+	  h2 = plot3 ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		      [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:),
+		      [zarrw1.'; zend.'; zarrw2.'; NaN(1, length (z))](:),
+		      "linestyle", "none");
+	else
+	  h2 = plot ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		     [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:),
+		     "linestyle", "none");
+	endif
+      else
+	if (is3d)
+	  h2 = plot3 ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		      [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:),
+		      [zarrw1.'; zend.'; zarrw2.'; NaN(1, length (z))](:),
+		      "linestyle", linespec.linestyle);
+	else
+	  h2 = plot ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		     [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:),
+		     "linestyle", linespec.linestyle);
+	endif
+      endif
+    elseif (is3d)
+      h2 = plot3 ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		  [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:),
+		  [zarrw1.'; zend.'; zarrw2.'; NaN(1, length (z))](:));
+    else
+      h2 = plot ([xarrw1.'; xend.'; xarrw2.'; NaN(1, length (x))](:),
+		 [yarrw1.'; yend.'; yarrw2.'; NaN(1, length (y))](:));
+    endif
+
+    if (! have_line_spec || (isfield (linespec, "marker") && 
+			     strncmp (linespec.marker, "none", 4)))
+      if (is3d)
+	h3 = plot3 (x, y, z, "linestyle", "none", "marker", "none");
+      else
+	h3 = plot (x, y, "linestyle", "none", "marker", "none");
+      endif
+    else
+      if (is3d)
+	h3 = plot3 (x, y, z, "linestyle", "none", "marker", linespec.marker);
+      else
+
+	h3 = plot (x, y, "linestyle", "none", "marker", linespec.marker);
+      endif
+    endif
+    if (have_filled)
+      ## FIXME gnuplot doesn't respect the markerfacecolor field
+      set(h3, "markerfacecolor", get (h1, "color")); 
+    endif
+  unwind_protect_cleanup
+    set (h, "nextplot", hstate);
+  end_unwind_protect
+
+  hlist = [h1; h2; h3];
+
+endfunction