Colony

function handles = plot_arrow( x1,y1,x2,y2,varargin )

%

% plot_arrow - plots an arrow to the current plot

%

% format:   handles = plot_arrow( x1,y1,x2,y2 [,options...] )

%

% input:    x1,y1   - starting point

%           x2,y2   - end point

%           options - come as pairs of "property","value" as defined for "line" and "patch"

%                     controls, see matlab help for listing of these properties.

%                     note that not all properties where added, one might add them at the end of this file.

%

%                     additional options are:

%                     'headwidth':  relative to complete arrow size, default value is 0.07

%                     'headheight': relative to complete arrow size, default value is 0.15

%                     (encoded are maximal values if pixels, for the case that the arrow is very long)

%

% output:   handles - handles of the graphical elements building the arrow

%

% Example:  plot_arrow( -1,-1,15,12,'linewidth',2,'color',[0.5 0.5 0.5],'facecolor',[0.5 0.5 0.5] );

%           plot_arrow( 0,0,5,4,'linewidth',2,'headwidth',0.25,'headheight',0.33 );

%           plot_arrow;   % will launch demo

% =============================================

% for debug - demo - can be erased

% =============================================

if (nargin==0)

    figure;

    set( gca,'nextplot','add' );

    for x = 0:0.3:2*pi

        color = [rand rand rand];

        h = plot_arrow( 1,1,50*rand*cos(x),50*rand*sin(x),...

            'color',color,'facecolor',color,'edgecolor',color );

        set( h,'linewidth',2 );

    end

    hold on;

    return

end

% =============================================

% end of for debug

% =============================================

% =============================================

% constants (can be edited)

% =============================================

alpha       = 0.15;   % head length

beta        = 0.07;   % head width

max_length  = 22;

max_width   = 10;

% =============================================

% check if head properties are given

% =============================================

% if ratio is always fixed, this section can be removed!

if ~isempty( varargin )

    for c = 1:floor(length(varargin)/2)

        try

            switch lower(varargin{c*2-1})

                % head properties - do nothing, since handled above already

            case 'headheight',alpha = max( min( varargin{c*2},1 ),0.01 );

            case 'headwidth', beta = max( min( varargin{c*2},1 ),0.01 );

            end

        catch

            fprintf( 'unrecognized property or value for: %s\n',varargin{c*2-1} );

        end

    end

end

% =============================================

% calculate the arrow head coordinates

% =============================================

den         = x2 - x1 + eps;                                % make sure no devision by zero occurs

teta        = atan( (y2-y1)/den ) + pi*(x2<x1) - pi/2;      % angle of arrow

cs          = cos(teta);                                    % rotation matrix

ss          = sin(teta);

R           = [cs -ss;ss cs];

line_length = sqrt( (y2-y1)^2 + (x2-x1)^2 );                % sizes

head_length = min( line_length*alpha,max_length );

head_width  = min( line_length*beta,max_length );

x0          = x2*cs + y2*ss;                                % build head coordinats

y0          = -x2*ss + y2*cs;

coords      = R*[x0 x0+head_width/2 x0-head_width/2; y0 y0-head_length y0-head_length];

% =============================================

% plot arrow  (= line + patch of a triangle)

% =============================================

h1          = plot( [x1,x2],[y1,y2],'k' );

h2          = patch( coords(1,:),coords(2,:),[0 0 0] );

% =============================================

% return handles

% =============================================

handles = [h1 h2];

% =============================================

% check if styling is required

% =============================================

% if no styling, this section can be removed!

if ~isempty( varargin )

    for c = 1:floor(length(varargin)/2)

        try

            switch lower(varargin{c*2-1})

             % only patch properties

            case 'edgecolor',   set( h2,'EdgeColor',varargin{c*2} );

            case 'facecolor',   set( h2,'FaceColor',varargin{c*2} );

            case 'facelighting',set( h2,'FaceLighting',varargin{c*2} );

            case 'edgelighting',set( h2,'EdgeLighting',varargin{c*2} );

            % only line properties

            case 'color'    , set( h1,'Color',varargin{c*2} );

            % shared properties

            case 'linestyle', set( handles,'LineStyle',varargin{c*2} );

            case 'linewidth', set( handles,'LineWidth',varargin{c*2} );

            case 'parent',    set( handles,'parent',varargin{c*2} );

            % head properties - do nothing, since handled above already

            case 'headwidth',;

            case 'headheight',;

            end

        catch

            fprintf( 'unrecognized property or value for: %s\n',varargin{c*2-1} );

        end

    end

end