chiliNUT chiliNUT - 1 year ago 59
Javascript Question

How can I rotate a pie chart in charts.js?

It looks like a pie in

is drawn by taking a vertical radius on the top half of the circle, and then moving clockwise from there. This works great most of the time, but for a pie with only 2 categories, it would be nice if it could be rotated so that the slice is centered, like this:

enter image description here

The rotation is calculated by taking the percentage of 360 and dividing by 2.
(.14*360)/2 = 25.2
degrees left, so if I could just apply

transform: rotate(-25.2deg);

to the circle I would be good.

puts this on a canvas (as opposed to
) I don't know how to apply any transformations to this. Not sure if relevant, but here is my code for the chart:


<canvas id=canvas style='width:300px;height:300px;'></canvas>


openRate = [
value: 488,
color: "#FF9030",
highlight: "rgba(255, 144, 48, 0.44)",
value: 3475,
color: "#008DB7",
highlight: "rgba(0, 141, 183, 0.82)"

var ctx=document.getElementById('canvas').getContext("2d");
var chart=new Chart(ctx).Pie(openRate);

And a fiddle:

Answer Source

You can rotate using CSS3:    JSFIDDLE DEMO

   -ms-transform: rotate(-25.2deg); /* IE 9 */
   -webkit-transform: rotate(-25.2deg); /* Chrome, Safari, Opera */
   transform: rotate(-25.2deg);