javascript/jquery build array from counted array

Question

Hey i have a simple question i cant find an answer, i´m trying to generate some raw-data for a chart

lets say i have an array like :

[1,0,0,1,2,0]

is there a way to make an array out of it that has nested arrays that represent the count of duplicate entrys ?

[[0,3],[1,2],[2,1]]

here is some code that does the trick, but saves the count as objects

var array = [1,0,0,1,2,0];
var length = array.length;
var objectCounter = {};

for (i = 0; i < length; i++) {

    var currentMemboerOfArrayKey = JSON.stringify(array[i]);

    var currentMemboerOfArrayValue = array[i];

    if (objectCounter[currentMemboerOfArrayKey] === undefined){

         objectCounter[currentMemboerOfArrayKey] = 1;
    }else{
        objectCounter[currentMemboerOfArrayKey]++;
    }
}

but objectCounter returns them like

{0:3,1:2,2:1}

but i need it as an array i specified above ?

for any help, thanks in advance

You can just convert it to an array with a forin loop. Or initialize with Array() — Manishearth
– Manishearth, Commented Dec 16, 2013 at 9:30

Arun P Johny · Accepted Answer · 2013-12-16 09:33:23Z

3

Try

var array = [1, 0, 0, 1, 2, 0];

function counter(array) {
    var counter = [],
        map = {}, length = array.length;
    $.each(array, function (i, val) {
        var arr = map[val];
        if (!arr) {
            map[val] = arr = [val, 0];
            counter.push(arr);
        }
        arr[1] += 1;
    })

    return counter;
}
console.log(JSON.stringify(counter(array)))

Demo: Fiddle

answered Dec 16, 2013 at 9:33

Arun P Johny

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2 Comments

john Smith Over a year ago

Yeah that for me is the perfect solution ! thank you very much and the others too

forsvunnet Over a year ago

Could you explain how this code works? I think it is quite interesting how you link map[val] and arr to the same array and how you've taken advantage of the closure to store the map variable.

Tibos · Accepted Answer · 2013-12-16 09:31:21Z

2

You can turn your object into an array easily:

var obj = {0:3,1:2,2:1};

var arr = [];
for (var key in obj) {
  // optional check against Object.prototype changes
  if (obj.hasOwnProperty(key)) {
    arr.push([+key, obj[key]]);
  }
}

Note: The object keys are strings, so i converted them back to numbers when placed in the array.

answered Dec 16, 2013 at 9:31

Tibos

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Comments

Tibos · Accepted Answer · 2013-12-16 09:46:20Z

2

Functional way of doing this, with Array.reduce and Array.map

var data = [1,0,0,1,2,0];

var result = data.reduce(function(counts, current) {
    counts[current] = current in counts ? counts[current] + 1: 1;
    return counts;
}, {});

result = Object.keys(result).map(function(current){
    return [parseInt(current), result[current]];
});
console.log(result);

Output

[ [ 0, 3 ], [ 1, 2 ], [ 2, 1 ] ]

edited Dec 16, 2013 at 9:46

Tibos

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answered Dec 16, 2013 at 9:43

thefourtheye

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2 Comments

i_made_that Over a year ago

Nice elegant, functional solution! How could I adapt it to work on, for example, an array of letters?

thefourtheye Over a year ago

@i_made_that What do you want as the output?

codingrose · Accepted Answer · 2013-12-16 09:32:42Z

1

Try:

var data = [1,0,0,1,2,0];
var len = data.length;
var ndata = [];
for(var i=0;i<len;i++){
    var count = 0;
    for(var j=i+1;j<len;j++){
        if(data[i] == data[i]){
            count ++;
        }
    }
    var a = [];
    a.push(data[i]);
    a.push(count);
    ndata.push(a);   
}
console.log(ndata)

DEMO here.

answered Dec 16, 2013 at 9:32

codingrose

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Comments

forsvunnet · Accepted Answer · 2013-12-16 09:39:36Z

1

First you need to map the array to an associative object

var arr = [1,0,0,1,2,0];
var obj = {};
for (var i = 0; i < arr.length; i++) {
  if (obj[arr[i]] == undefined) {
    obj[arr[i]] = 0;
  }
  obj[arr[i]] += 1;
}

Then you can easily turn that object into a 2d matrix like so:

arr = [];
for (var k in obj) {
  arr.push([k, obj[k]]);
}

alert(JSON.stringify(arr));

answered Dec 16, 2013 at 9:39

forsvunnet

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Comments

nnnnnn · Accepted Answer · 2013-12-16 09:40:08Z

1

Your existing object can be turned into an array with a simple for..in loop. Also your existing code that produces that object can be simplified. Encapsulate both parts in a function and you get something like this:

function countArrayValues(array) {
  var counter = {},
      result = [];

  for (var i = 0, len = array.length; i < len; i++)
    if (array[i] in counter)
      counter[array[i]]++;
    else
      counter[array[i]] = 1;

  for (i in counter)
    result.push([+i, counter[i]]);

  return result;
}

console.log( countArrayValues([1,0,0,1,2,0]) );

Demo: http://jsfiddle.net/hxRz2/

answered Dec 16, 2013 at 9:40

nnnnnn

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