clc;clear;
% setup data
h = 0.01;
e = 0.001;
x = (0:h:1);
% normal bump
y = exp(-(x-0.3).^2/0.05^2) + e*randn(size(x));
% very wild stuff
% y = sin(40*x);
plot(x,y)
p = randperm(numel(x));
x = x(p);
y = y(p);
plot(x,y,'-b',x,y,'or');

% check:
x = x-min(x); x=x/max(x);
y = y-min(y); y=y/max(y);


[~,ix] = sort(x);
[~,iy] = sort(y);
d1 = sum(sqrt(diff(x(ix)).^2 + diff(y(ix)).^2));
d2 = sum(sqrt(diff(x(iy)).^2 + diff(y(iy)).^2));

disp('negative difference = flipped:')
disp([d2-d1, d2, d1]);