#! perl -slw
use strict;
use GD::Graph::lines;
use GD::Graph::colour qw(:colours :lists :files :convert);
use Data::Dump qw[ pp ];
use List::Util qw[ sum ];

our $MOVES ||= 4;
our $SRAND ||= 1;

srand $SRAND; ## Allow consistancy between runs for testing

my $y = 30 * int rand 6; ## A base level for the random data 
my @data = map[], 1..4;

my @moving; ## to hold the last $MOVING values for averaging

## Every 3 minutes throughout a day
for my $x ( 0 .. (24 * 20 -1 ) ) {

    ## Generate Y values varies randomly around the current transition level 
    ## (which varies randomly see below)
    my $actualY = $y + -30 + int( rand 60 );

    push @{ $data[ 0 ] }, $x / 20; ## X values in decimal hours
    push @{ $data[ 1 ] }, $y; ## display the random baseline in red
    push @{ $data[ 2 ] }, $actualY; ## The actual values in green

    ## Store the LAST $MOVES values
    push @moving, $actualY;
    shift @moving if $#moving >= $MOVES ;

    ## Calculate the moving average
    my $ave = sum( @moving ) / $MOVES;

    ## and round it to the nearest transition level
    $ave = 30 * ( int( ( $ave + 15 ) / 30 ) );
    push @{ $data[ 3 ] }, $ave; ## display it in blue

    ## Make a random change to the base level 20% of the time
    next if rand > 0.2;
    $y = ( int( $y / 30 ) + ( -1 + int rand 3 ) ) * 30;
    $y = 30 if $y < 30;
    $y = 150 if $y > 150;
}

#pp \@data; <>;

my $file = '789655.png';

my $graph = GD::Graph::lines->new(3000, 768);

$graph->set(
    'bgclr' => 'white',
    'transparent' => 0,
    'interlaced' => 1,

    title             => 'Some simple graph',

    x_label           => 'X Label',
    x_max_value => 24,
    x_min_value => 0,
    x_tick_number => 24,

    y_label           => 'Y label',
    y_max_value       => 180,
    y_min_value       => 0,
    y_tick_number     => 12,
    y_label_skip      => 2,

) or die $graph->error;

my $gd = $graph->plot(\@data) or die $graph->error;

open IMG, '>', $file or die $!;
binmode IMG;
print IMG $gd->png;
close IMG;

system $file; ## Load the graph into the local default image viewer

__END__
Usage: 789655.pl -MOVES=5  ##(less than 3 or > 10 not good )