timestampex01.php

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    <?php // content="text/plain; charset=utf-8"
    // Example on how to treat and format timestamp as human readable labels
    require_once ('jpgraph/jpgraph.php');
    require_once ('jpgraph/jpgraph_line.php');

    // Number of "fake" data points
    DEFINE('NDATAPOINTS',500);

    // Assume data points are sample every 10th second
    DEFINE('SAMPLERATE',10);

    // Callback formatting function for the X-scale to convert timestamps
    // to hour and minutes.
    function TimeCallback($aVal) {
        return Date('H:i', $aVal);
    }

    // Get start time
    $start = time();
    // Set the start time to be on the closest minute just before the "start" timestamp
    $adjstart = floor($start / 60);

    // Create a data set in range (20,100) and X-positions
    // We also apply a simple low pass filter on the data to make it less
    // random and a little smoother
    $data = array();
    $xdata = array();
    $data[0] = rand(20,100);
    $xdata[0] = $adjstart;
    for( $i=1; $i < NDATAPOINTS; ++$i ) {
        $data[$i] = rand(20,100)*0.2 + $data[$i-1]*0.8;
        $xdata[$i] = $adjstart + $i * SAMPLERATE;
    }

    // Assume that the data points represents data that is sampled every 10s
    // when determing the end value on the scale. We also add some extra
    // length to end on an even label tick.
    $adjend = $adjstart  + (NDATAPOINTS+10)*10;

    $graph = new Graph(500,250);
    $graph->SetMargin(40,20,30,50);

    // Now specify the X-scale explicit but let the Y-scale be auto-scaled
    $graph->SetScale("intlin",0,0,$adjstart,$adjend);
    $graph->title->Set("Example on TimeStamp Callback");

    // Setup the callback and adjust the angle of the labels
    $graph->xaxis->SetLabelFormatCallback('TimeCallback');
    $graph->xaxis->SetLabelAngle(90);

    // Set the labels every 5min (i.e. 300seconds) and minor ticks every minute
    $graph->xaxis->scale->ticks->Set(300,60);

    $line = new LinePlot($data,$xdata);
    $line->SetColor('lightblue');
    $graph->Add($line);

    $graph->Stroke();
    ?>