5.11. Example - Points Plot with Error Bars
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## 5.11. Example - Points Plot with Error Bars

This is a point plot with error bars (as indicated by data type 'data-data-error'). Each point is specified as X value, Y value, Y error in the positive direction, and Y error in the negative direction.

Example 5.11. Points Plot with Error Bars

    <?php
    # PHPlot Example: Point chart with error bars
    require_once 'phplot.php';

    $data = array(
      array('', 1,  23.5, 5, 5), array('', 2,  20.1, 3, 3),
      array('', 3,  19.1, 2, 2), array('', 4,  16.8, 3, 3),
      array('', 5,  18.4, 4, 6), array('', 6,  20.5, 3, 2),
      array('', 7,  23.2, 4, 4), array('', 8,  23.1, 5, 2),
      array('', 9,  24.5, 2, 2), array('', 10, 28.1, 2, 2),
    );

    $plot = new PHPlot(800, 600);
    $plot->SetImageBorderType('plain');

    $plot->SetPlotType('points');
    $plot->SetDataType('data-data-error');
    $plot->SetDataValues($data);

    # Main plot title:
    $plot->SetTitle('Points Plot With Error Bars');

    # Set data range and tick increments to get nice even numbers:
    $plot->SetPlotAreaWorld(0, 0, 11, 40);
    $plot->SetXTickIncrement(1);
    $plot->SetYTickIncrement(5);

    # Draw both grids:
    $plot->SetDrawXGrid(True);
    $plot->SetDrawYGrid(True);  # Is default

    # Set some options for error bars:
    $plot->SetErrorBarShape('tee');  # Is default
    $plot->SetErrorBarSize(10);
    $plot->SetErrorBarLineWidth(2);

    # Use a darker color for the plot:
    $plot->SetDataColors('brown');
    $plot->SetErrorBarColors('brown');

    # Make the points bigger so we can see them:
    $plot->SetPointSizes(10);

    $plot->DrawGraph();

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