function example1(params)
% example function puts a simple gui on the screen that draws some markers
% call it without parameters: type draw

% check if the folders "units" and "tools" are in the path. If not, do it
% automatically.
% Please put them in the path permanently with file/set path...
extra_path

% check the number of inputs
if nargin==0 % initial call without parameters.
params=parameter('drawing parameters'); % create an object of the parameter class with name
% now we add some items to it:
params=add(params,'panel','select shape',3); % a panel is a square around the following (in this case 3) items
params=add(params,'radiobutton','square'); % three radiobuttons
params=add(params,'radiobutton','circle',1); % this one is selected
params=add(params,'radiobutton','other...'); % here the user can make its own choice
params=add(params,'slider','radius',unit_length,5,'cm',0,10); % a slider value with the unit "length". watch what happens!
% params=setcallback(params,'radius','example1(params)'); % try this!
% params=add(params,'float','radius',unit_length,5,'cm',0,inf); % a float value with the unit "length". watch what happens!
params=add(params,'bool','hold on','true'); % a tick box that is set to true
params=add(params,'button','clear','figure(1),cla;'); % first button: clear the figure
params=add(params,'button','draw','example1(params)'); % second button calls the drawing part of the function

figure(1) % opens new figure
parametergui(params); % create the gui
return % and return to the shell. From now on the gui has the control
end

% if we are here then we are called from the gui with the parameter
% structure in "params"

figure(1) % always work in the same figure
% check the value of the tick box. Get it by its name:
if get(params,'hold on') % returns the value of the item in params with the name 'hold on'
hold on
else
clf
end

% we plot a shape in the figure. Lets see how big the user wants it.
% get the entry of the float field as units poits (not exactly cm but close enough...)
radius=getas(params,'radius','point');
switch get(params,'select shape') % get the currently selected radiobutton
case 'circle'
mark='o';
case 'triangle'
mark='^';
otherwise % non of the two above. It must be the 'other...' value
mark=get(params,'select shape'); % get the string in the "other..." line
end
% and finally plot something
plot(0,0,'markersize',radius,'marker',mark);

%wait for further commands from the gui...