pChart Radar chart with minimum 1

I'm using a Radar Chart similar to this example: https://pchart.net/doc.draw.radar.html

My data ranges from score 1 to 4, so I configured some options:

$options = array(
    'SegmentHeight' => 1,
    'Segments' => 3,
    'FixedMax' => 4
);

One problem remains: Even if my lowest score is 1, the Radar chart always has the value 0 in the center.

How can I change the minimum value in the chart to 1?