How to display percentage to the d3.js piechart

Question

I have summed up the dataset using nest,rollup and d3.sum functions and I'm able to display the pie chart properly.But I'm unable display percentage for each slice based on the summed total.Can anyone please give suggestions on this issue...

 Mycode:
 ======
   d3.csv("pi.csv", function(error, csv_data) {
         var data = d3.nest()
          .key(function(d) { return d.ip;})
          .rollup(function(d) {
           return d3.sum(d, function(g) {return g.value; });
          }).entries(csv_data);

        data.forEach(function(d) {
         d.ip= d.key;
         d.value = d.values;
        });

        My dataset:
        =========
        ip,timestamp,value
        92.239.29.77,1412132430000,3190
        92.239.29.77,1412142430000,319011
        92.239.29.78,1412128830000,545568
        92.239.29.78,1412130600000,616409
        92.239.29.78,1412132430000,319087
        92.239.29.76,1412130600000,616409
        92.239.29.76,1412132430000,319087

Thanks in advance

Answer 1

So it seems that you want to display the percentage of each pie slice on the chart. All you really need to do is to calculate the the total of the values and iterate across the data variable adding in the percentage.

The data.forEach function doesn't add anything to the data variable, so I would drop that. I should also point out that the d3.nest function rolls up and sums each individual ip entry, so you're not getting sum of all values. However, this is pretty easy to do with d3, you can just use d3.sum:

var tots = d3.sum(data, function(d) { 
            return d.values; 
        });

Once you've done that you iterate across the data variable like:

data.forEach(function(d) {
    d.percentage = d.values  / tots;
});

You can then access the percentage on each pie slice using something like d.data.percentage

And putting it all together.

Note you could also compute the percentage from the start and end angles for each slice: (d.endAngle - d.startAngle)/(2*Math.PI)*100.