How to filter d3.nested data in javascript - nested function

Question

I am trying to filter to get value by nested data so if my input is ... enter image description here

currently I use the code below to get b from maximum a for each name ( christine, smiths, aaron ) . But I am trying to get value b where a = 2 for each name ( christine, hannah, jeannie)

  var names = d3.nest()
      .key(function(d) { return d.name; })
      .entries(data);

   names.forEach(function(n) {
    n.maxAValue = d3.max(n.values, function(d) { return d.b; });
                             });

the above works fine, but I was trying to get value where a == 2 with something like this below. Is there a way I could do something like this in javascript ?

names.forEach(function(n) { n.values, 
       function(d) { if(d.a == 2) { return d.b; }  }
                          });

======Edit======

data = [
  {
    "name":"apple",
    "a":1,
    "b":"jame"
  },
  {
    "name":"apple",
    "a":2,
    "b":"christine"
  },
  {
    "name":"orange",
    "a":1,
    "b":"nick"
  },
  {
    "name":"orange",
    "a":2,
    "b":"hannah"
  },
  {
    "name":"orange",
    "a":3,
    "b":"smiths"
  },
  {
    "name":"peach ",
    "a":1,
    "b":"boo"
  },
  {
    "name":"peach ",
    "a":2,
    "b":"jeannie"
  },
  {
    "name":"peach ",
    "a":3,
    "b":"aaron"
  }
]

To filter data in any kind of way, I like to use lodash, it helps a lot with array manipulation. — Hugues Stefanski
– Hugues Stefanski, Commented Mar 9, 2015 at 19:59
@HuguesStefanski can you show me exactly how to do this in my case, i 'm fairly new to javascript. .. — JPC
– JPC, Commented Mar 9, 2015 at 20:02
Would you happpen to have your data in json format? Or maybe a plunk/jsbin already? — Hugues Stefanski
– Hugues Stefanski, Commented Mar 9, 2015 at 20:06
Plnkr using lodash: plnkr.co/edit/PfgQjwAmbz4JxTyZBxaB?p=preview — Hugues Stefanski
– Hugues Stefanski, Commented Mar 9, 2015 at 20:21

David Anderson · Accepted Answer · 2015-03-09 20:18:48Z

3

You can use the built-in array.filter function for this:

var filtered = data.filter(function(d) {
   return d.a == 2; 
});

Here's a JSFiddle that demonstrates this in action and then uses d3 to bind the filtered data to an HTML ul:

http://jsfiddle.net/bywdq375/1/

answered Mar 9, 2015 at 20:18

David Anderson

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