d3.nest adding extra variables

问题

I just wanted to add two new variables in the below data i.e., slope and intersect. data.csv file contains only the listed columns - Levels, X, Y and Size. I wanted to add two new variables mentioned above in the below data.

Data :

    [
          {
            "key": "Level1",
            "values": [
              {
                "x": 118,
                "y": 106,
                "size": 1.113207547
              },
              {
                "x": 111,
                "y": 137,
                "size": 0.810218978
              },
              {
                "x": 144,
                "y": 195,
                "size": 0.738461538
              },
              {
                "x": 116,
                "y": 129,
                "size": 0.899224806
              },
              {
                "x": 117,
                "y": 119,
                "size": 0.983193277
              },
              {
                "x": 145,
                "y": 122,
                "size": 1.18852459
              }
            ],
             "slope": 0.52289599949494,
            "intercept": 0.2795214697252959
          },
          {
            "key": "Level2",
            "values": [
              {
                "x": 172,
                "y": 193,
                "size": 0.89119171
              },
              {
                "x": 138,
                "y": 114,
                "size": 1.210526316
              },
              {
                "x": 106,
                "y": 189,
                "size": 0.560846561
              },
              {
                "x": 123,
                "y": 141,
                "size": 0.872340426
              },
              {
                "x": 129,
                "y": 110,
                "size": 1.172727273
              },
              {
                "x": 162,
                "y": 198,
                "size": 0.818181818
              }
            ],
             "slope": 0.52289599949494,
            "intercept": 0.2795214697252959
          },
          {
            "key": "Level3",
            "values": [
              {
                "x": 191,
                "y": 104,
                "size": 1.836538462
              },
              {
                "x": 177,
                "y": 186,
                "size": 0.951612903
              },
              {
                "x": 106,
                "y": 140,
                "size": 0.757142857
              },
              {
                "x": 131,
                "y": 161,
                "size": 0.813664596
              },
              {
                "x": 111,
                "y": 128,
                "size": 0.8671875
              },
              {
                "x": 149,
                "y": 122,
                "size": 1.221311475
              },
              {
                "x": 200,
                "y": 126,
                "size": 1.587301587
              }
            ],
             "slope": 0.52289599949494,
            "intercept": 0.2795214697252959
          }
        ]

Tried with the below function :

    d3.csv("data.csv", function(data) {

                    data.forEach(function(d) {
                        d.x = +d.x
                        d.y = +d.y
                        d.size = +d.size
                    })

                    //var type = ['Basic Phone', 'Featured Phone', 'Smart Phone']

                    var nest = d3.nest()
                                .key(function(d) {return d.type;})
                                .rollup(function(v) {return v.map(function(d) {delete d.type; return d; d.slope = Math.random(), d.intersent = Math.random()})})
                                .entries(data);

                   d3.select('body').append('pre')
                   .text(JSON.stringify(nest, null, '  '));
                })  

回答1:

After getting the output from the nest.entries(), you can iterate that array and add your properties:

nest.forEach(function (d) { 
    d.slope = Math.random(); 
    d.intercept = Math.random(); 
})

回答2:

function(d) {delete d.type; return d; d.slope = Math.random(), d.intersent = Math.random()}

is equivalent to

function(d) {delete d.type; return d;}

What follows return doesn't get to be executed. Try

function(d) {delete d.type; d.slope = Math.random(), d.intersent = Math.random(); return d; }

来源：https://stackoverflow.com/questions/19833322/d3-nest-adding-extra-variables