Question

I have got a json file like so:

[
 {"id":1,"sex":"Female","programming":5, "project":7}, 
 {"id":2,"sex":"Male","programming":8, "project":4}, 
 {"id":3,"sex":"Female","programming":5, "project":6}, 
 {"id":4,"sex":"Male","programming":4, "project":7} 
]

I want to calculate the mean of the value’s of programming with D3 js
I can get the total mean of it like so:

function meanVak(value) {
    return d3.mean(data, function(d) {return d [value] })
}

var meanProgramming = meanVak('programming');

But now i want a separate mean for ‘programming’ based on sex. So for female and male.
How should i do that?

Answer 1

// I think the easiest way is to use the d3.nest function.  Perhaps something like ... 
var nest = d3.nest()
  .key(function(d) { return d.sex; })
  .sortKeys(d3.ascending)
  .rollup(function(d) {
    return {
      meanVakValue: d3.mean(d, function(g) { return g[value]; })
    };
  })
  .map(data);

// You may then need to turn it back into entries.  I had to use map first then extract to entries
// but I'm still getting my head around d3.
var nestedData = d3.entries(nest);