D3.nest（）循环键

Question

Data = [{s1: xx , s2: xx , … , s200: xx} ,  
[{s1: xx , s2: xx , … , s200: xx} ,  
….
[{s1: xx , s2: xx , … , s200: xx} ]

_.keys(data[0]) will get [“s1”,”s2”,…,”s200”]

totals = d3.nest().rollup(function(v){ return {
  s1 : d3.sum(v, function(d){ return d.s1;}),
  s2 : d3.sum(v, function(d){ return d.s2;}),
…..
  s200 : d3.sum(v, function(d){ return d.s200;})
};}).entries(data);

如何通过循环键获得总数，即不逐一列出键？

Answer 1

你可以这样做：

var keys = Object.keys(Data[0]); // save array of keys to variable

var totals = d3.nest().rollup(function(v){
  var result = {};

  keys.forEach(function(key) { // for each key
    result[key] = d3.sum(v, function(d){ return d[key];}); // set appriptiate property with sum of this key
  });

  return result;
}).entries(Data);