function rankclock(rank,varargin)
  % RANKCLOCK - Make rank clock plot
%
% RANKCLOCK(rank, options) plots the diagram based on the rank data in the matrix rank. Each row
% contains the subsequent rank values for one entity. NaN is allowed and will produce breaks
% in the plot.
% 
% Options can be added:
% 'labels' takes the following array of numbers as numerical labels for the spokes.
% 'plabels' followed by a cell array allows labelling the entities
% 'gap' leaves open a gap between the last and first spoke
% 'mark' followed by an array marks the nonzero entries
% 'markwidth' followed by a number sets the line width of marked entries
% 'whitening' followed by a number in [0,1] sets the greyout of unmarked entries.
% 'rect' makes the plot rectangular
% 'invert' turns the plot inside out.
% 'background' followed by a [r g b] array sets the bacground color.
%
  plotlabels=0;
  gap=0;
  mark=0;
  linew=2;
  rect=0;
  invert=0;
  linelabels=0;
  whitening=.75;
  background=0;

  for j=1:size(varargin,2)
    if (strcmp(varargin{j},'labels')==1)
      label=varargin{j+1};
      plotlabels=1;
    end
    if (strcmp(varargin{j},'plabels')==1)
      plabel=varargin{j+1};
      linelabels=1;
    end
    if (strcmp(varargin{j},'gap')==1)
      gap=1;
    end
    if (strcmp(varargin{j},'mark')==1)
      mark=1;
      marked=varargin{j+1};
    end
    if (strcmp(varargin{j},'markwidth')==1)
      linew=varargin{j+1};
    end
    if (strcmp(varargin{j},'whitening')==1)
      whitening=varargin{j+1};
    end
    if (strcmp(varargin{j},'rect')==1)
      rect=1;
    end
    if (strcmp(varargin{j},'invert')==1)
      rank=max(rank(:))-rank+1;
    end
    if (strcmp(varargin{j},'background')==1)
      background=1;
      bc=varargin{j+1};
    end
  end
  
  
  N=size(rank,1);
  M=size(rank,2);
  
  theta=-pi/2+(0:(M-1))*2*pi/(M-1+gap);
  
  firstrank=zeros(N,1);
  first=zeros(N,1);
  for i=1:N
    j=1;
    while(firstrank(i)==0)
      if (~isnan(rank(i,j)))
	firstrank(i)=rank(i,j);
	first(i)=j;
	continue
      end
      j=j+1;
    end
  end


  
  col=jet(max(rank(:)));
  col=col(firstrank,:);
  
  if (mark==1)
    for i=1:N
      if (marked(i)==1)
	1,
      else
	col(i,:)=col(i,:)*(1-whitening)+whitening;
      end
    end
  end

  clf
  hold on 
  axis off
  axis square

  if (background==1)
    R=max(rank(:))*1.3;
    if (rect==0)
      l=patch(R*[-1; 1; 1; -1],R*[-1; -1; 1; 1],bc)
      axis([-R R -R R]*1.001)
    else
      l=patch([min(theta); max(theta); max(theta); min(theta)],max(rank(:))*[0; 0; 1; 1],bc)
      axis([min(theta) max(theta(:)) 0 R])      
    end
  end

  for i=1:N
    if (rect==0)
      l=polar(-theta,rank(i,:));
    else
      l=plot(theta,rank(i,:));
    end
    set(l,'Color',col(i,:));
    if (mark==1)
      if (marked(i)==1)
	set(l,'LineWidth',linew);
      end
    end
  end

  for i=1:N
    if (linelabels==1 & (mark==0 | (mark == 1 & marked(i)==1)))
      if (rect==0)
	text(rank(i,first(i))*cos(-theta(first(i))),rank(i,first(i))*sin(-theta(first(i))),char(plabel(i)));
      else
	text(theta(first(i)),rank(i,first(i)),char(plabel(i)));
      end
    end
  end
  
  if (plotlabels==1)
    N2=max(rank(:))*1.1;
    for i=1:M
      if (rect==0)
	text(N2*cos(-theta(i)),N2*sin(-theta(i)),sprintf('%d',label(i)));
      else
	text(theta(i),-2,sprintf('%d',label(i)));
      end
    end
  end