D3.js Donut transition

Question

I am working on a d3 donut and am stuck on how to update the donut value where the value will flow back if for instance you change the value from 42 to 17. I can remove the svg, but then it rewrites the new value (17) from the zero position.

I would like it to flow backwards from 42 say to 17.

var path = svg.selectAll("path")
        .data(pie(dataset.lower))
        .enter().append("path")
        .attr("class", function(d, i) { return "color" + i })
        .attr("d", arc)
        .each(function(d) { this._current = d; }); // store the initial values

here is a link to my jsfidle http://jsfiddle.net/yr595n96/

and I would love any help you could offer.

Thanks

Answer 1

Heres you're new button click :

$("#next").click(function () {
    percent = 17;
    var progress = 0;
    var timeout = setTimeout(function () {
        clearTimeout(timeout);
        var randNumber = Math.random() * (100 - 0 + 1) + 0;
        //path = path.data(pie(calcPercent(17))); // update the data << change this
        path = path.data(pie(calcPercent(randNumber)));
        path.transition().duration(duration).attrTween("d", function (a) {
            // Store the displayed angles in _current.
            // Then, interpolate from _current to the new angles.
            // During the transition, _current is updated in-place by d3.interpolate.
            var i  = d3.interpolate(this._current, a);
            var i2 = d3.interpolate(progress, randNumber)
            this._current = i(0);
            return function(t) {
                text.text( format(i2(t) / 100) );
                return arc(i(t));
            };
        }); // redraw the arcs
    }, 100);
});

Notice on line '8':

path = path.data(pie(calcPercent(randNumber)));

You need to pass new data for it to transition to. I have used a random number here just to show you any number works. I made a variable for this and passed it to both the 'path' and the text : 'i2' > d3.interpolate.

You can always just change it to 17 to suit what you asked for :)

Updated fiddle : http://jsfiddle.net/yr595n96/3/