function plot_Xing(fname, levels, isTimeSeries, isIncremental)

% plot sample path and crossings, and crossing tree
%
% fname: input file name without extension, x(t(n)) and t(n) in files fname.dat and fname.tim
% isTimeSeries: if 1 then t(n) = n and fname.tim not used
% isIncremental: if 1 then fname.dat contains x(n) - x(n-1)
% levels: levels to be plotted
%
% Y.Shen 12.2002, O.D.Jones 7.2003

eval(['load ' fname '.dat;']);
eval(['x = ' fname '(:,1);']);
if isTimeSeries
    if isIncremental
        x = [0; cumsum(x)];
    end
    lx = length(x);
    t = 0:lx-1;
else
    lx = length(x);
    eval(['load ' fname '.tim;']);
    eval(['t = ' fname '(:,1);']);
end

clf

subplot(2,1,1);
hold on;
plot(t, x, 'g');
title('sample path and crossings')

subplot(2,1,2);
hold on;
title('crossing tree (points give start of crossing)')
ylabel('crossing size')

for n = levels
    if n < 10
        file_name = sprintf('%s_0%d', fname, n);
    else
        file_name = sprintf('%s_%d', fname, n);
    end
    eval(['load ' file_name '.hit;']);
    eval(['data = ' file_name ';']);
    if ~isempty(data)
        subplot(2,1,1);
        plot(data(:,1), data(:,2), 'b');
        plot(data(:,1), data(:,2), 'b.');
        subplot(2,1,2);
        plot(data(1:end-1,1), 2^n, 'b.');
        if n ~= levels(1)
            for i = 1:size(data,1)-1
                jj  = find((data0(:,1) >= data(i,1)) & (data0(:,1) < data(i+1,1)));
                for j = jj'
                    plot([data(i,1), data0(j,1)], [2^n, 2^n0], 'b');
                end
            end
        end        
        data0 = data;
        n0 = n;
    end
end

subplot(2,1,1);
hold off;

subplot(2,1,2);
hold off;