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"Chia C Chong" <Chia.Chong@ee.ed.ac.uk> wrote in message
news:b5dur7$8qi$1@scotsman.ed.ac.uk...
> Hi there!
>
> I wish to draw a double head arrow (i.e. <------> ) in Matlab to show a
> section of the graph. But it seems to me, Matlab only allows arrow with a
> single head (i.e. ------>). So, my question is what should I do so that I
> can draw a double head arrow?
>
> Thanks.
>
> CCC
>
>
Here is _yet another_ arrow function.
The big drawback of all arrow fucntions I've tried is that changing the axis
scale distorts the arrow.
This arrow function (below) allows all arrows in all functions to be redrawn
to be correctly displayed after one or more axis scales have changed, simply
by typing "arrow".
FWIW,
Aj
------------- begin arrow.m -------------
function hh=arrow5(varargin)
%ARROW Draw an arrow.
% ARROW(tail,head) draw an arrow between the tail (x,y) and head (x,y)
%
%
ARROW(tail,head,'Property1',PropertyValue1,'Property2',PropertyValue2,...)
% draw an arrow, and sets the values of the specified properties of the
arrow.
%
% ARROW('Property1',PropertyValue1,'Property2',PropertyValue2,...)
% draw an arrow, and set the values of the specified properties of the
arrow.
% The 'head' and 'tail' properties must be specified.
%
% ARROW(H,'Property1',PropertyValue1,'Property2',PropertyValue2,...)
% sets the values of the specified properties of an existing arrow.
%
% H = ARROW(...) returns the handle to the line object used as the arrow.
%
% ARROW redraws all arrows (rescaling if required). This may affect the
% the values of gca and gcf.
%
% Additional properties supported are:
% 'size' length of the arrow head, in inches (default 0.125)
% 'direction' direction of the arrow, 'forward', 'backward', or
'double'
% 'angle' angle of the arrowhead
% 'tail' define [x,y] of tail of arrow
% 'head' define [x,y] of head of arrow
%
% NOTES: The arrowhead is scaled to be drawn correctly when printed. It
may
% appear skewed in the figure window. Also, any of the following may
cause
% existing arrows to be rendered improperly:
% - the axes 'position' is changed
% - the axes 'xlim' or 'ylim' is changed
% - the figure 'PaperPosition' is changed
% In general, it is recommended that arrows be drawn last.
% Use ARROW with no arguments to redraw all arrows
h = [];
head = [];
tail = [];
if nargin == 0
redraw_all_arrows; % sub-fuction speified below
return
end
if mod(nargin,2) == 0
% Even number of arguments
if isreal(varargin{1}) & isreal(varargin{2})
head = varargin{1};
tail = varargin{2};
varargin(1:2) = [];
end
else
% Odd number of arguments
if isreal(varargin{1})
% First arg is is: hopefully handle(s) to existing arrow(s)
h = varargin{1};
tag = get(h,'tag');
if ~strcmp(tag,'arrow')
error('Handle must an existing arrow')
end
varargin(1) = [];
varargin = [get(h,'userdata'),varargin];
else
error('Incorrect number of input arguments')
end
end
keeplist = [];
discardlist = [];
headsize = 0.125;
ang = 15; % Angle of arrow
direction = 'forward';
for i=1:2:length(varargin)
if ~isstr(varargin{i})
error('Invalid property name');
else
switch lower(varargin{i})
case 'direction', direction = varargin{i+1};
case 'size', headsize = varargin{i+1};
case 'angle', ang = varargin{i+1};
case 'head', head = varargin{i+1};
case 'tail', tail = varargin{i+1};
otherwise, keeplist = [keeplist,i,i+1];
end
end
end
varargin = varargin(keeplist);
x1 = head(1);
x2 = tail(1);
y1 = head(2);
y2 = tail(2);
% x=[head(1),tail(1)]
% y=[head(2),tail(2)]
if length(h) == 0
h = plot([x1 x2],[y1 y2]); % Plot the basic arrow line
a = gca; % Parent axes handle
f = gcf; % Parent figure handle
else
a = get(h,'parent');
f = get(a,'parent');
end
xlim = get(a,'xlim');
ylim = get(a,'ylim');
xd = diff(xlim);
yd = diff(ylim);
ppos_inch = get(f,'PaperPosition'); % Figure position on paper, in inches
(left, bottom, width, height)
apos_norm = get(a,'Position'); % Axes position on figure, normalized
apos_inch = [
ppos_inch(1)+apos_norm(1)*ppos_inch(3),
ppos_inch(2)+apos_norm(2)*ppos_inch(4),
apos_norm(3)*ppos_inch(3),
apos_norm(4)*ppos_inch(4)];
xscale = xd/apos_inch(3);
yscale = yd/apos_inch(4);
len = sqrt(sum((head-tail).^2)); % Length of arrow
baseline = (tail-head)./len; % unit vector long baseline
baseline = baseline(1)/xscale+j*baseline(2)/yscale;
baseline = baseline ./ abs(baseline);
orient = headsize.*exp(j*ang*pi/180);
p1=orient.*baseline;
p2=conj(orient).*baseline;
xp1=real(p1)*xscale;
yp1=imag(p1)*yscale;
xp2=real(p2)*xscale;
yp2=imag(p2)*yscale;
if strcmp(direction, 'backward') | strcmp(direction, 'double')
x = [x1,x1+xp1,x1,x1+xp2,x1];
y = [y1,y1+yp1,y1,y1+yp2,y1];
else
x=[x1];
y=[y1];
end
if strcmp(direction, 'forward') | strcmp(direction, 'double')
x = [x, x2,x2-xp1,x2,x2-xp2,x2];
y = [y, y2,y2-yp1,y2,y2-yp2,y2];
else
x = [x, x2];
y = [y, y2];
end
userdata = {'tail', tail, 'head', head, 'direction', direction, 'size',
headsize, 'angle', ang};
set(h,'tag','arrow','userdata',userdata,'xdata',x','ydata',y,varargin{:});
if nargout > 0
hh = h;
end
return
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function redraw_all_arrows(varargin)
for f=get(0,'children')' % Loop over all figures
for a=get(f,'children')' % Loop over all axes
h_list = get(a,'children');
for h=h_list' % Loop over all types
Type = get(h,'Type');
if isstr(Type) & strcmp(Type,'line')
if strcmp(get(h,'Tag'),'arrow') & length(get(h,'userdata')) > 6
args = [{h},varargin];
arrow(args{:}); % Redraw arrow
end
end
end
end
end
----------- end arrow ------------
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