function varargout=mySplacement(varargin)

global a;
global magp;
global phasep;
global impulsep;
global splanep;
global placepoles placezeroes newpole showsurface showcookie surfacefig shownormalisedfreq;
global clearpoles donenewpole N;
%evalin('caller','if ~exist(''zeroes'') global zeroes; end;')
evalin('caller','global zeroes;')
global zeroes;
if (isempty(zeroes)) zeroes=[]; end;
%evalin('caller','if ~exist(''poles'') global poles; end;') 
evalin('caller','global poles;') 
global poles;
if (isempty(poles)) poles=[]; end;

if nargin == 0
    action = 'init';
%    shh = get(0,'ShowHiddenHandles');
%    set(0,'ShowHiddenHandles','on')
%    spfig = findobj(0,'Tag','sptool');
%    set(0,'ShowHiddenHandles',shh);
%    if ~isempty(spfig)
%        figure(spfig)
%        return
%    end
else
    action = varargin{1};
	eval(action);
end

%[a,magp,phasep,impulsep,splanep]=placementS;                        

switch action

case 'init'
	
% AJL STUFF (GLOBAL FLAGS)
placepoles = 0; % we are noew playing with pole placement
placezeroes = 1; % we are now playing with zero placement
newpole = 0; % used to store a button press location on the zplane
showsurface = 0; % show the z transform as a surface in separate figure
showcookie = 0; % show the unit circle only as surface in sepearate figure
surfacefig = 0; % seperate figure handle for surface drawing
shownormalisedfreq = 0; % show in the seperate figure the freqz output
%poles = []; % list of current poles
%zeroes = []; % list of current zeros
clearpoles = 1; % whether to zero the list
donenewpole = 0; % a flag
if ~isempty(poles)	
    clearpoles = 0;
	donenewpole = 1;
else
    poles = []; % list of current poles
end;
if ~isempty(zeroes)
    clearpoles = 0;
	donenewpole = 1;
else
    zeroes = []; % list of current poles
end;
N = 128; % number of samples in impulse response

[a,magp,phasep,impulsep,splanep]=placementS;                        


% AJL STUFF (MAIN LOOP)
%axes(splanep);
%if findstr(version,'5.2') == 1
%  set(splanep,'Color',[ 0 0 0]);
%end;
%axis([-2 2 -2 2]);
%sgrid;
%c = get(splanep,'Children');
%for i=1:length(c)
%	set(c,'Color',[0 0 0.5]);
%end;
%drawnow;
if clearpoles == 1
   mySplacement('clearpoles = 1;'); % recursively call back to get first draw
else
	mySplacement('clearpoles = 0; donenewpole = 1;'); % recursively call back to get first draw
end;

% AJL always do this part
otherwise

  if clearpoles ~= 0
    disp('Clearing all poles and zeroes');
    clearpoles = 0;
    poles = [];
    zeroes = [];

	end;

 if newpole ~= 0  
    newpole =0;
    donenewpole = 1;  
%    disp('Placing a singularity');
    figure(a);
    axes(splanep);

    polelocation = ginput(1)

    if placepoles ~= 0
       if polelocation(2) == 0
         poles = [poles; (polelocation(1) + j*0)];
        else
         poles = [poles;  (polelocation(1) + j*polelocation(2))];
         poles = [poles;  (polelocation(1) - j*polelocation(2))];
        end;
      end;
    if placezeroes ~= 0
        if polelocation(2) == 0
         zeroes = [zeroes; (polelocation(1) +j*0)];
        else
         zeroes = [zeroes; (polelocation(1) + j*polelocation(2))];
         zeroes = [zeroes; (polelocation(1) - j*polelocation(2))];
        end;
      end;
  
  end;
  
    % work out the impulse response by first finding the freq response
    theimpulseresponse = zeros(1,N);
    theimpulseresponse(1) = 1;
    numerator = poly(zeroes);
    denominator = poly(poles);
    
    freqsamples = linspace(-2,2,N);
    [dft,freqsamples]=freqs(numerator,denominator,freqsamples);

    theimpulseresponse=fftshift(ifft(fftshift(dft)));

    axes(splanep);
    hold off;
    cla;
    if findstr(version,'5.2') == 1
	  set(splanep,'Color',[ 0 0 0]);
    end;
    axis([-2 2 -2 2]);
    sgrid;
%	c = get(splanep,'Children');
%	for i=1:length(c)
%		set(c,'Color',[0 0 0.5]);
%	end;
    hold on;
%    pzmap(poles,zeroes);
     if poles ~= []
        plot(poles,'*r')
    end
    hold on;
    if zeroes ~= []
        plot(zeroes,'og')
    end
    
    axis([-1 1 -1 1]);
   hold off;
    axes(magp);
    plot(freqsamples,abs(dft));

    axes(phasep);
    plot(freqsamples,angle(dft));

    axes(impulsep);
    plot(real(theimpulseresponse));
    drawnow;

  if showsurface ~= 0
    showsurface = 0;
    if surfacefig ~= 0 
       figure(surfacefig);
    else
       surfacefig = figure;
    end;
    rationaltransformplot(poles,zeroes,2,'log');
    drawnow;
 elseif showcookie ~= 0
    showcookie = 0;
    if surfacefig ~= 0 
       figure(surfacefig)
    else
       surfacefig = figure;
    end;
    rationaltransformplot(poles,zeroes,2,'sfreqonly');
    drawnow;
  elseif ((shownormalisedfreq ~= 0)&(donenewpole ~=0))
    donenewpole = 0;
    if surfacefig ~= 0 
       figure(surfacefig)
    else
       surfacefig = figure;
    end;
    bode(numerator,denominator);
    drawnow;
    figure(a);
  end;
end;