<?php // content="text/plain; charset=utf-8"
require_once 'jpgraph/jpgraph.php';
require_once 'jpgraph/jpgraph_line.php';

// Callback to negate the argument
function _cb_negate($aVal)
{
    return round(-$aVal);
}

// A fake depth curve
$ydata = array(0, 1, 4, 5, 8, 9, 10, 14, 16, 16, 16, 18, 20, 20, 20, 22, 22.5, 22, 19, 19, 15, 15, 15, 15, 10, 10, 10, 6, 5, 5, 5, 4, 4, 2, 1, 0);

$n      = count($ydata);
$y2data = array();
for ($i = 0; $i < $n; ++$i) {
    $y2data[] = $ydata[$i] + 10;
}

// Negate all data
$n = count($ydata);
for ($i = 0; $i < $n; ++$i) {
    $ydata[$i]  = round(-$ydata[$i]);
    $y2data[$i] = round(-$y2data[$i]);
}

// Basic graph setup
$graph = new Graph\Graph(400, 300);
$graph->SetScale("linlin");
$graph->SetY2Scale("lin");
$graph->SetMargin(50, 50, 60, 40);
$graph->SetMarginColor('darkblue');
$graph->SetColor('darkblue');

// Setup titles
$graph->title->Set("Inverting both Y-axis");
$graph->title->SetFont(FF_FONT1, FS_BOLD);
$graph->title->SetColor("white");

$graph->subtitle->Set("(Negated Y & Y2 axis)");
$graph->subtitle->SetFont(FF_FONT1, FS_NORMAL);
$graph->subtitle->SetColor("white");

// Setup axis
$graph->yaxis->SetLabelFormatCallback("_cb_negate");
$graph->xaxis->SetColor("lightblue", "white");
$graph->yaxis->SetColor("lightblue", "white");
$graph->ygrid->SetColor("blue");

// Setup Y2 axis
$graph->y2axis->SetLabelFormatCallback("_cb_negate");
$graph->y2axis->SetColor("darkred", "white");
$graph->y2scale->SetAutoMax(0); // To make sure it starts with 0

// Setup plot 1
$lp1 = new Plot\LinePlot($ydata);
$lp1->SetColor("yellow");
$lp1->SetWeight(2);
$graph->Add($lp1);

// Setup plot 2
$lp2 = new Plot\LinePlot($y2data);
$lp2->SetColor("darkred");
$lp2->SetWeight(2);
$graph->AddY2($lp2);

$graph->Stroke();
