c3.js total count in title of pie chart - sum

Question

I have a question about the pie chart in c3.js.
How can I add the total count of a pie chart in the title??
var title = new Array('data1.sql','data2.sql')
var dtitle = new Array('title1','title2')
var chart = new Array('chart0', 'chart1')
for(var i = 0; i < title.length; i++){
chart[i] = c3.generate({
bindto : '#chart' + i,
size: {
height: 550,
width: 800
},
data : {
url : '/json/sql/data/test/' + title[i],
mimeType : 'json',
type : 'donut'
},
donut: {
title: dtitle[i] + ' - Total:' ,
label: {
format: function(value, ratio, id) {
return value;
}
}
}
});
}

Answer 1

The annoying thing here is that the title option can take a function, but the chart variable is not initialised within it so using the c3 api methods can't be done at this point.
So the best (maybe only) way is to add an onrendered callback that adds up the data as you'd need to anyways and then replace the text in the chart's title text using a spot of d3:
onrendered: function () {
var data = this.api.data();
var total = data.reduce (function (subtotal, t) {
return subtotal + t.values.reduce (function (subsubtotal,b) { return subsubtotal + b.value; }, 0);
}, 0);
d3.select(this.config.bindto + " .c3-chart-arcs-title").text("Total: "+total);
}
Edit: If you want it to keep track of a total as you hide/show series use this
var data = this.api.data.shown.call (this.api);
instead of
var data = this.api.data();