How to draw "double head arrow"?

Chia C Chong — Fri, 21 Mar 2003 02:53:16 -0500

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

Re: How to draw "double head arrow"?

Dan Hensley — Fri, 21 Mar 2003 04:06:27 -0500

On Fri, 21 Mar 2003 02:53:16 +0000, Chia C Chong wrote:

> 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

Why not draw one on top of the other, pointing in opposite directions?

Dan

Re: How to draw "double head arrow"?

Chia C Chong — Fri, 21 Mar 2003 13:07:12 -0500

So, is it means that there is actually no single function that allows me to
draa double-arrow in Matlab??

CCC

"Dan Hensley" <danDOThensley@attbi.com> wrote in message
news:pan.2003.03.21.04.06.26.258442@attbi.com...
> On Fri, 21 Mar 2003 02:53:16 +0000, Chia C Chong wrote:
>
> > 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
>
> Why not draw one on top of the other, pointing in opposite directions?
>
> Dan

Re: How to draw "double head arrow"?

us — Fri, 21 Mar 2003 08:38:52 -0500

you may want to look at a nice <spotlight> by former (?)
TMW/CSSMer <nabeel> (wehre is he?) at

<http://www.mathworks.com/matlabcentral/spotlight/arrows.shtml>

us

Chia C Chong wrote:
> 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. ------>).

Re: How to draw "double head arrow"?

us — Fri, 21 Mar 2003 08:42:17 -0500

us wrote:
> you may want to look at a nice <spotlight> by former (?)
> TMW/CSSMer <nabeel> (wehre is he?)

i'm terribly sorry! i just realized that the <spotlight> was
created by <ned gulley>.

us

Re: How to draw "double head arrow"?

AJ \"no z\" Johnson — Fri, 21 Mar 2003 10:30:57 -0500

"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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