how to calculate the angle between the mid of a clicked donut element and the negative y-axis

Question

Consider the following codesample donut chart using jquery-flot , now as i have added the \'image\' class on click of the donut, i want to dynamically add the degree in the \'im

Answer 1

Here you can find my solution to your problem if I got you right.

$("#pie-placeholder").bind("plotclick", function(event, pos, obj) {
if (obj) {
    var percentInRads = 0.02;
    var currSegmentInRads = percentInRads * obj.datapoint[0]
    var currSegmentOffset = currSegmentInRads / 2;
    var currSegmentStart = currSegmentOffset >= 0.5 ? -0.5 + currSegmentOffset : 0.5 - currSegmentOffset;
    var total = 0;
    var beforeTotal = 0;

    for (var idx = 0; idx < data.length; idx++) {
      var segment = data[idx];

      if (idx < obj.seriesIndex) {
        beforeTotal += segment.data;
      }

      total += segment.data;
    }

    var beforePart = (beforeTotal / total * 100) * percentInRads;
    var chartStartAngle = currSegmentStart - beforePart;

    options.series.pie.startAngle = chartStartAngle;
    $.plot($("#pie-placeholder"), data, options);
    console.log(obj.series);
}

});