d3.js: sort nested arrays

Question

How can I sort the nested arrays of an array like the one below please? I would like to sort array prob and then rearrange name accordingly so that relationship is maintained.

var records = [
{ num: 1, name: ["Sam", "Amy", "John"], prob: [0.3, 0.2, 0.5]},
{ num: 2, name: ["Nick", "Carol", "Sam"], prob: [0.5, 0.03, 0.47] },
{ num: 3, name: ["Ken", "Eric", "Ely"], prob: [0.1, 0.3, 0.6] },
{ num: 4, name: ["Amy", "Sam", "John"], prob: [0.6, 0.3, 0.1] },
{ num: 5, name: ["Chris", "Donna", "Jeff"], prob: [0.25, 0.55, 0.2] }
]

I would like to end-up with:

var records = [
{ num: 1, name: ["John", "Sam", "Amy"], prob: [0.5, 0.3, 0.2]},
{ num: 2, name: ["Nick", "Sam", "Carol"], prob: [0.5, 0.47, 0.03] },
{ num: 3, name: ["Ely", "Eric", "Ken"], prob: [0.6, 0.3, 0.1] },
{ num: 4, name: ["Amy", "Sam", "John"], prob: [0.6, 0.3, 0.1] },
{ num: 5, name: ["Donna", "Chris", "Jeff"], prob: [0.55, 0.25, 0.2] }
]

Thanks!

combine the elements of name and prop in an array of objects with name and prop properties. sort this array by prop, create the name and prop array from this sorted array of objects — rioV8
– rioV8, Commented Sep 5, 2018 at 14:21
Can you clarify "name accordingly so that relationship is maintained.". How are you sorting the names array (in what order). — Ankit
– Ankit, Commented Sep 5, 2018 at 14:26

Emeeus · Accepted Answer · 2018-09-05 16:08:02Z

1

Here a solution: we could store names and prob in pairs and sorting both values at the same time, then we assign that names and probs sorted to the main object:

var records = [
{ num: 1, name: ["Sam", "Amy", "John"], prob: [0.3, 0.2, 0.5]},
{ num: 2, name: ["Nick", "Carol", "Sam"], prob: [0.5, 0.03, 0.47] },
{ num: 3, name: ["Ken", "Eric", "Ely"], prob: [0.1, 0.3, 0.6] },
{ num: 4, name: ["Amy", "Sam", "John"], prob: [0.6, 0.3, 0.1] },
{ num: 5, name: ["Chris", "Donna", "Jeff"], prob: [0.25, 0.55, 0.2] }
];

var pairs = records.map((e,i)=>
e.name.map((e2,i2)=>[e2,records[i].prob[i2]]).sort((a,b)=>b[1]-a[1])
);

records.map((e, i) => {
  e.name = pairs[i].map(o => o[0])
  e.prob = pairs[i].map(o => o[1])      
})

console.log(records)

edited Sep 5, 2018 at 16:08

answered Sep 5, 2018 at 15:41

Emeeus

5,2922 gold badges30 silver badges42 bronze badges

Sign up to request clarification or add additional context in comments.

7 Comments

rioV8 Over a year ago

what is the need to keep the intermediate results of pairs?

Emeeus Over a year ago

@rioV8 to sort both values at the same time

rioV8 Over a year ago

No. Just sort el. indentation helps readability. and ; are also helpful, construct el with .map()

rioV8 Over a year ago

el is an array you can sort, === e you use in pairs.forEach

Emeeus Over a year ago

another good point @rioV8, thanks. I was too focused on the main logic

|

rioV8 · Accepted Answer · 2018-09-05 15:55:33Z

1

Refactoring Emeeus answer

var records = [
{ num: 1, name: ["Sam", "Amy", "John"], prob: [0.3, 0.2, 0.5]},
{ num: 2, name: ["Nick", "Carol", "Sam"], prob: [0.5, 0.03, 0.47] },
{ num: 3, name: ["Ken", "Eric", "Ely"], prob: [0.1, 0.3, 0.6] },
{ num: 4, name: ["Amy", "Sam", "John"], prob: [0.6, 0.3, 0.1] },
{ num: 5, name: ["Chris", "Donna", "Jeff"], prob: [0.25, 0.55, 0.2] }
];

records.forEach((e, i) => {
  var el = e.name.map((e2,i2)=>[e2,e.prob[i2]]);
  el.sort((a, b) => b[1] - a[1]);
  e.name = el.map(o => o[0]);
  e.prob = el.map(o => o[1]);
});

console.log(records);

answered Sep 5, 2018 at 15:55

rioV8

29.7k4 gold badges48 silver badges68 bronze badges

Comments

i alarmed alien · Accepted Answer · 2018-09-05 16:51:15Z

1

It's easiest if you turn your arrays of names and probs into objects to preserve the links between each name and the probability. The object's properties can then be sorted as if they were an array using a custom sort function.

records.forEach( function (d) {
  var temp = {};

  // create objects with key <name> and value <prob>
  // (this makes the assumption that prob values may not be unique, but names are)
  d.name.forEach( function(e,i) {
    temp[e] = d.prob[i];
  })

  // get an array of the object keys (the name), and sort them by the object values
  // (the corresponding prob), descending. Replace the existing `name` array with this.
  d.name = Object.keys(temp).sort(function(a, b){ 
    return temp[b] - temp[a];
  });

  // sort the prob values in descending order (with d3.descending, since you mentioned d3)
  d.prob = d.prob.sort(function(a,b){ return b - a; });
});

If you aren't using d3, replace d3.descending with the standard descending sort function.

edited Sep 5, 2018 at 16:51

answered Sep 5, 2018 at 15:26

i alarmed alien

9,5403 gold badges30 silver badges40 bronze badges

3 Comments

rioV8 Over a year ago

using 2 different sorting methods and both hard coded is waiting for a very hard to track bug if the code is modified. Use the same sorting function.

i alarmed alien Over a year ago

d3.descending performs the same sorting function as a standard numeric sort.

Aenaon Over a year ago

thanks a lot everyone, this is what i ended up with, pretty much what rioV8 and Emmeus proposed: var out = []; for (var i=0; i<records.length; i++) { t = d3.zip(records[i].name, records[i].prob); t.sort(function (a, b) { return b[1] - a[1]; }); var name = t.map(function (d, i) { return d[0] }); var prob = t.map(function (d, i) { return d[1] }); out.push({ num: records[i].num, name: name, prob: prob, }); }

Collectives™ on Stack Overflow

d3.js: sort nested arrays

3 Answers 3

7 Comments

Comments

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

7 Comments

Comments

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related