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Last active December 19, 2023 11:14
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Pie Chart Update, II
license: gpl-3.0

This variation of a donut chart demonstrates how to update values with an animated transition. Clicking on the radio buttons changes the displayed metric.

Next: Missing Data
Previous: Static Update

apples oranges
53245 200
28479 200
19697 200
24037 200
40245 200
<!DOCTYPE html>
<meta charset="utf-8">
<style>
body {
font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
margin: auto;
position: relative;
width: 960px;
}
text {
font: 10px sans-serif;
}
form {
position: absolute;
right: 10px;
top: 10px;
}
</style>
<form>
<label><input type="radio" name="dataset" value="apples" checked> Apples</label>
<label><input type="radio" name="dataset" value="oranges"> Oranges</label>
</form>
<script src="//d3js.org/d3.v3.min.js"></script>
<script>
var width = 960,
height = 500,
radius = Math.min(width, height) / 2;
var color = d3.scale.category20();
var pie = d3.layout.pie()
.value(function(d) { return d.apples; })
.sort(null);
var arc = d3.svg.arc()
.innerRadius(radius - 100)
.outerRadius(radius - 20);
var svg = d3.select("body").append("svg")
.attr("width", width)
.attr("height", height)
.append("g")
.attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");
d3.tsv("data.tsv", type, function(error, data) {
if (error) throw error;
var path = svg.datum(data).selectAll("path")
.data(pie)
.enter().append("path")
.attr("fill", function(d, i) { return color(i); })
.attr("d", arc)
.each(function(d) { this._current = d; }); // store the initial angles
d3.selectAll("input")
.on("change", change);
var timeout = setTimeout(function() {
d3.select("input[value=\"oranges\"]").property("checked", true).each(change);
}, 2000);
function change() {
var value = this.value;
clearTimeout(timeout);
pie.value(function(d) { return d[value]; }); // change the value function
path = path.data(pie); // compute the new angles
path.transition().duration(750).attrTween("d", arcTween); // redraw the arcs
}
});
function type(d) {
d.apples = +d.apples;
d.oranges = +d.oranges;
return d;
}
// 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.
function arcTween(a) {
var i = d3.interpolate(this._current, a);
this._current = i(0);
return function(t) {
return arc(i(t));
};
}
</script>
@whiter4bbit
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function arcTween(a) {
  var i = d3.interpolate(this._current, a);
  /*
   *  I think, that it makes sense to change to this._current = i(1) to store latest transition, it works now, because of
   *  references. Change this._current = jQuery(this, {}, i(0)); will break animation.
   */
  this._current = i(0);
  return function(t) {
    return arc(i(t));
  };
} 

@bmaland
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bmaland commented Apr 8, 2014

Here's a jsbin version: http://jsbin.com/hegob/1/edit?js,output

@mcordingley
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Shouldn't line 85 read this._current = i(1); to set the value for the next update? I don't see how "_current is updated in-place by d3.interpolate".

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