#!/usr/bin/perl
use strict;
use warnings;

my @points;
for (1 .. 100) {
    my $x = rand()**2;
    my $y = function($x);
    my $dy = 0.01 + $x*0.1*rand()**2;
    $y += offset($dy);
    push @points, [map sprintf("%.4f", $_), $x, $y, $dy];
}

$, = "\n";
$" = "\t";
print map("@$_", @points), "\n";


sub function {
    my ($x) = @_;
    return 0.25 + 0.75*(1-$x)**0.25;
}

sub offset {
    my ($x) = @_;
    return $x*(rand()-0.5)*exp(rand());
}