root/gliderproc/trunk/MATLAB/plots/arrowsafe.m

function [x, y] = arrowsafe(x0, y0, theLength, theAngle, theHeadSize)

% arrowsafe -- Intelligent, oriented arrows.
%  arrowsafe('demo') demonstrates itself with arrows centered
%   on the origin, each one-unit long.
%  arrowsafe(N) demonstrates itself with N arrows.
%  arrowsafe(x0, y0, theLength, theAngle, theHeadSize) draws
%   arrows that start at (x0, y0), with theLength (in y-axis units),
%   theAngle (degrees, counter-clockwise from +x), and theHeadSize
%   (in y-axis units).  The variables should be the same size, but
%   any can be a scalar, just so long as the x0 and/or y0 array is
%   the full size.  The "ResizeFcn" of the figure is set to update
%   the arrows automatically.  The "Tag" is the mfilename.
%  h = arrowsafe(...) draws the arrows and returns the handle.
%  [x, y] = arrowsafe(...) returns the (x, y) data for the
%   arrows, one column per arrow, but does not draw them.
%  arrowsafe (no argument) redraws existing arrows. This is
%   useful whenever the window is resized or the x or y limits
%   change.  (Recall that printing causes the "ResizeFcn" to
%   be called twice.)
%
%
% Calls: none
% Note: this routine leaves the axes in "manual" mode.  Use
%  "axis auto" to revert to automatic axis limits.
 
% Copyright (C) 2000 Dr. Charles R. Denham, ZYDECO.
%  All Rights Reserved.
%   Disclosure without explicit written consent from the
%    copyright owner does not constitute publication.
 
% Version of 12-Jan-2000 14:22:59.
% Updated    22-Aug-2001 08:46:00.

RCF = 180 / pi;

% Resize.

if nargin < 1
        oldGCA = gca;
        h = findobj(gcf, 'Type', 'line', 'Tag', mfilename);
        for i = 1:length(h)
                p = get(h(i), 'Parent');
                axes(p)
                u = get(h(i), 'UserData');
                [xx, yy] = feval(mfilename, u(:, 1), u(:, 2), ...
                                                        u(:, 3), u(:, 4), u(:, 5));
                set(h(i), 'XData', xx(:), 'YData', yy(:));
        end
        axes(oldGCA)
        return
end

% Demonstration.

if nargin == 1
        if isequal(x0, 'demo')
                help(mfilename)
                x0 = 16;
        elseif ischar(x0)
                x0 = eval(x0);
        end
        theName = [mfilename ' demo'];
        f = findobj('Type', 'figure', 'Name', theName);
        if ~any(f)
                f = figure('Name', theName);
        end
        figure(max(f))
        delete(get(f, 'Children'))
        n = max(1, round(x0));
        x0 = zeros(1, n);
        ang = linspace(0, 360, length(x0)+1);
        ang(end) = [];
        h = feval(mfilename, x0, 0, 1, ang);
        set(gca, 'Xlim', [-n n], 'YLim', [-2 2])
        feval(mfilename)
        set(gcf, 'WindowButtonDownFcn', ...
                        ['if zoomsafe(''down''), ' mfilename ', end'])
        if nargout > 0, x = h; end
        return
end

% Initialize.

if nargin > 1
        if nargout == 2, x = []; y = []; end
        if length(x0) == 1
                x0 = x0 * ones(size(y0));
        elseif length(y0) == 1
                y0 = y0 * ones(size(x0));
        end
        x0 = reshape(x0, [1 prod(size(x0))]);
        y0 = reshape(y0, size(x0));
        if nargin < 3, theLength = 1; end
        if nargin < 4, theAngle = 0; end
        if nargin < 5, theHeadSize = 0.1 .* theLength; end
        if length(theLength) == 1
                theLength = theLength * ones(size(x0));
        end
        if length(theAngle) == 1
                theAngle = theAngle * ones(size(x0));
        end
        if length(theHeadSize) == 1
                theHeadSize = theHeadSize * ones(size(x0));
        end

        theLength = reshape(theLength, size(x0));
        theAngle = reshape(theAngle, size(x0));
        theHeadSize = reshape(theHeadSize, size(x0));

        axes(gca)
        oldUnits = get(gca, 'Units');
        set(gca, 'Units', 'pixels')
        thePosition = get(gca, 'Position');
        set(gca, 'Units', oldUnits)
        theWidth = thePosition(3);   % pixels.
        theHeight = thePosition(4);   % pixels.
        
        axis('manual')
        dx = diff(get(gca, 'XLim'));
        dy = diff(get(gca, 'YLim'));
        dydx = dy / dx;   % Not used.
        dxdp = dx / theWidth;   % sci/pixel.
        dydp = dy / theHeight;   % sci/pixel.
        scale = dxdp / dydp;

        xa = [-10; -20; 0; -20; -10]/20;   % Arrowhead.
        ya = [0; 10; 0; -10; 0]/20;
        
        m = length(xa);
        n = prod(size(x0));
        repeats = [m 1];
        
        ang = repmat(theAngle, repeats);
        len = repmat(theLength, repeats);
        head = repmat(theHeadSize, repeats);
        
        xa = repmat(xa, [1 n]);
        ya = repmat(ya, [1 n]);
        
        xa = xa .* head;
        ya = ya .* head;
        
        xa = xa + len;
        
        za = xa + sqrt(-1) * ya;
        
        za = [zeros(1, n); za];
        
        ang = repmat(theAngle, [size(za, 1) 1]);
        len = repmat(theLength, [size(za, 1) 1]);
        head = repmat(theHeadSize, [size(za, 1) 1]);
        xx0 = repmat(x0, [size(za, 1) 1]);
        yy0 = repmat(y0, [size(za, 1) 1]);
        
        za = exp(sqrt(-1) * ang / RCF) .* za;
        
        xx = real(za) + xx0;
        yy = imag(za) + yy0;
        
        nans = zeros(1, n) + NaN;
        
        xx = [xx; nans];
        yy = [yy; nans];

        zz = xx + sqrt(-1) .* yy;

        xx0 = repmat(x0, [size(zz, 1) 1]);
        yy0 = repmat(x0, [size(zz, 1) 1]);

        xx = xx0 + real(zz) * scale;
        yy = yy0 + imag(zz);
        
        parameters = [x0(:) y0(:) theLength(:) theAngle(:) theHeadSize(:)];
        
        if nargout < 2
                h = line(xx(:), yy(:), ...
                        'Tag', mfilename, ...
                        'UserData', parameters);
                if nargout > 1, x = h; end
        elseif nargout == 2
                x = xx;
                y = yy;
        end
        set(gcf, 'ResizeFcn', mfilename)
        
        if nargout == 1, x = h; end
end