5.49. Example - Horizontal Error Plot
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## 5.49. Example - Horizontal Error Plot

This is a horizontal error plot, showing a series of measurements as a 'points' plot, with error bars. In a horizontal plot, the Y (vertical) axis is for the independent values, and the X axis (horizontal) is for the dependent values.

Note: Horizontal error plots were added in PHPlot-6.1.0.

Example 5.49. Horizontal Error Plot

    <?php
    # PHPlot Example - Horizontal Error Plot
    require_once 'phplot.php';

    # The experimental results as a series of temperature measurements:
    $results = array(98, 102, 100, 103, 101, 105, 110, 108, 109);
    # The accuracy of our measuring equipment is +/- 5%
    $error_factor = 0.05;

    # Convert the experimental results to a PHPlot data array for error plots.
    function reduce_data($results, $error_factor)
    {
        # Use the average of measurements to approximate the error amount:
        $err = $error_factor * array_sum($results) / count($results);

        # Build the 'data-data-yx-error' data array:
        $data = array();
        $i = 1;
        foreach ($results as $value) {
            $data[] = array("Sample $i", $i++, $value, $err, $err);
        }
        return $data;
    }

    $plot = new PHPlot(800, 600);
    $plot->SetTitle('Experiment Results');
    $plot->SetXTitle('Melting Temperature (degrees C)');
    $plot->SetDataValues(reduce_data($results, $error_factor));
    $plot->SetDataType('data-data-yx-error');
    $plot->SetPlotType('points');
    $plot->SetYTickPos('none');
    $plot->SetImageBorderType('plain'); // Improves presentation in the manual
    $plot->SetPlotAreaWorld(80);
    $plot->DrawGraph();

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5.48. Example - Horizontal Linepoints Plot with Data Value Labels and Lines | Home | 5.50. Example - Box Plot with Data Reduction