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comparison scripts/plot/compass.m @ 7322:40a17a87155e

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[project @ 2007-12-18 21:32:10 by jwe]
author jwe
date Tue, 18 Dec 2007 21:34:26 +0000
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7321:359f464342b3 7322:40a17a87155e
1 ## Copyright (C) 2007 David Bateman
2 ##
3 ## This file is part of Octave.
4 ##
5 ## Octave is free software; you can redistribute it and/or modify it
6 ## under the terms of the GNU General Public License as published by
7 ## the Free Software Foundation; either version 3 of the License, or (at
8 ## your option) any later version.
9 ##
10 ## Octave is distributed in the hope that it will be useful, but
11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 ## General Public License for more details.
14 ##
15 ## You should have received a copy of the GNU General Public License
16 ## along with Octave; see the file COPYING. If not, see
17 ## <http://www.gnu.org/licenses/>.
18
19 ## -*- texinfo -*-
20 ## @deftypefn {Function File} {} compass (@var{u}, @var{v})
21 ## @deftypefnx {Function File} {} compass (@var{z})
22 ## @deftypefnx {Function File} {} compass (@dots{}, @var{style})
23 ## @deftypefnx {Function File} {} compass (@var{h}, @dots{})
24 ## @deftypefnx {Function File} {@var{h} =} compass (@dots{})
25 ##
26 ## Plot the @code{(@var{u}, @var{v})} components of a vector field emanating
27 ## from the origin of a polar polt. If a single complex argument @var{z} is
28 ## given, then @code{@var{u} = real (@var{z})} and @code{@var{v} = imag
29 ## (@var{z})}.
30 ##
31 ## The style to use for the plot can be defined with a line style @var{style}
32 ## in a similar manner to the line styles used with the @code{plot} command.
33 ##
34 ## The optional return value @var{h} provides a list of handles to the
35 ## the parts of the vector field (body, arrow and marker).
36 ##
37 ## @example
38 ## @group
39 ## a = toeplitz([1;randn(9,1)],[1,randn(1,9)]);
40 ## compass (eig (a))
41 ## @end group
42 ## @end example
43 ##
44 ## @seealso{plot, polar, quiver, feather}
45 ## @end deftypefn
46
47 function retval = compass (varargin)
48
49 [h, varargin, nargin] = __plt_get_axis_arg__ ("compass", varargin{:});
50
51 arrowsize = 0.25;
52 firstnonnumeric = Inf;
53 for i = 1:nargin
54 if (! isnumeric (varargin{i}))
55 firstnonnumeric = i;
56 break;
57 endif
58 endfor
59
60 if (nargin < 2 || firstnonnumeric < 2)
61 ioff = 2;
62 z = varargin {1} (:) .';
63 u = real (z);
64 v = imag (z);
65 else
66 ioff = 3;
67 u = varargin {1} (:) .';
68 v = varargin {2} (:) .';
69 endif
70
71 line_spec = "b-";
72 while (ioff <= nargin)
73 arg = varargin{ioff++};
74 if ((isstr (arg) || iscell (arg)) && ! have_line_spec)
75 [linespec, valid] = __pltopt__ ("compass", arg, false);
76 if (valid)
77 line_spec = arg;
78 break;
79 else
80 error ("compass: invalid linespec");
81 endif
82 else
83 error ("compass: unrecognized argument");
84 endif
85 endwhile
86
87 ## Matlab draws compass plots, with the arrow head as one continous
88 ## line, and each arrow separately. This is completely different than
89 ## quiver and quite ugly.
90 n = length (u);
91 xend = u;
92 xtmp = u .* (1 - arrowsize);
93 yend = v;
94 ytmp = v .* (1 - arrowsize);
95 x = [zeros(1, n); xend; xtmp - v * arrowsize / 3; xend; ...
96 xtmp + v * arrowsize / 3];
97 y = [zeros(1, n); yend; ytmp + u * arrowsize / 3; yend; ...
98 ytmp - u * arrowsize / 3];
99 [r, p] = cart2pol (x, y);
100
101 oldh = gca ();
102 unwind_protect
103 axes (h);
104 newplot ();
105 hlist = polar (h, r, p, line_spec);
106 unwind_protect_cleanup
107 axes (oldh);
108 end_unwind_protect
109
110 if (nargout > 0)
111 retval = hlist;
112 endif
113
114 endfunction
115
116 %!demo
117 %! a = toeplitz([1;randn(9,1)],[1,randn(1,9)]);
118 %! compass (eig (a))