function [x,y] = plotlevelgrid(p)
% FUNCTION:    plotlevelgrid                Part of DPWT Toolbox
%
% SYNOPSIS:    [X,Y] = plotlevelgrid(P)
%
% DESCRIPTION: For integer P corresponding to the log2 of 
%              the length of a wavelet coordinate vector
%              plotlevelgrid plots a map of the wavelet 
%              coordinates at levels -1 through P-1
%              indicating by their position along the
%              abscissa the position of the center of the
%              inverse wavelet transform corresponding to 
%              that coordinate. Level numbers appear
%              along the ordinant. Length is assumed to be 
%              between 0 and 1. X and Y contain the plot
%              coordinates of the coordinate marks.
%
% NOTE:        This function is mainly designed for use by plotwaveletcoords.
%
% EXAMPLE:     w = randn(2^7,1);
%              plotlevelgrid(8);
%

%
% AUTHOR:     Neil Getz
% DATE:       5-11-92
%
% COPYRIGHT 1992, Neil Getz
%

if(nargin ~=1),
  help plotlevelgrid;
  return;
end;
 
clg,
x = zeros(1,2^p - 1);
y = x; % for size
for level = 0:(p-1),
  x(2^(level):(2^(level+1) - 1)) ...
  	= [1:2:( 2^(level+1) - 1 )] * 2^(-(level+1));
  y(2^(level):(2^(level+1) - 1)) = level*ones(1,2^level);
end;
x = [1/2,x];
y = [-1,y];
for i = -1:(p-1),
	h = line([0 1], [i i]);
	set(h,'Color','b');
end
axis([0 1 -2 p]);

ylabel('Level');