example16.6.php

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    <?php // content="text/plain; charset=utf-8"
    require_once ("jpgraph/jpgraph.php");
    require_once ("jpgraph/jpgraph_scatter.php");
    require_once ("jpgraph/jpgraph_line.php");
    require_once ("jpgraph/jpgraph_utils.inc.php");

    // Create some "fake" regression data
    $datay = array();
    $datax = array();
    $a= 3.2;
    $b= 2.5;
    for($x=0; $x < 20; ++$x) {
        $datax[$x] = $x;
        $datay[$x] = $a + $b*$x + rand(-20,20);
    }

    $lr = new LinearRegression($datax, $datay);
    list( $stderr, $corr ) = $lr->GetStat();
    list( $xd, $yd ) = $lr->GetY(0,19);

    // Create the graph
    $graph = new Graph(300,250);
    $graph->SetScale('linlin');

    // Setup title
    $graph->title->Set("Linear regression");
    $graph->title->SetFont(FF_ARIAL,FS_BOLD,14);

    $graph->subtitle->Set('(stderr='.sprintf('%.2f',$stderr).', corr='.sprintf('%.2f',$corr).')');
    $graph->subtitle->SetFont(FF_ARIAL,FS_NORMAL,12);

    // make sure that the X-axis is always at the
    // bottom at the plot and not just at Y=0 which is
    // the default position
    $graph->xaxis->SetPos('min');

    // Create the scatter plot with some nice colors
    $sp1 = new ScatterPlot($datay,$datax);
    $sp1->mark->SetType(MARK_FILLEDCIRCLE);
    $sp1->mark->SetFillColor("red");
    $sp1->SetColor("blue");
    $sp1->SetWeight(3);
    $sp1->mark->SetWidth(4);

    // Create the regression line
    $lplot = new LinePlot($yd);
    $lplot->SetWeight(2);
    $lplot->SetColor('navy');

    // Add the pltos to the line
    $graph->Add($sp1);
    $graph->Add($lplot);

    // ... and stroke
    $graph->Stroke();

    ?>