A box and whisker chart is useful for displaying the distribution of a dataset. A whisker chart visualizes the median, first quartile, third quartile and the lowest and highest value in one plot.

To use a Box & Whisker chart, your dataset must be specified in a special way - it need to know the datasets for which to calulate the distributions. This is done by replacing the y-value with the set of data (in the form of a simple array), i.e.

$Dataset =& Image_Graph::factory('dataset');
$Dataset->addPoint(
    'set 1',
    array(10, 12, 9, 15, 13, 11, 12, 17, 14)
);
 
$Dataset->addPoint(
    'set 2',
    array(12, 21, 13, 16, 15, 19, 20, 16, 21, 12, 14)
);

And then simply create the Box & Whisker plot based on this dataset.

$Plot =& $Plotarea->addNew('Image_Graph_Plot_BoxWhisker', $Dataset);

Image_Graph Example