How to optimize array grouping?

Question

I have an array that is constantly updated and accordingly it is necessary to update its grouping. Example of an array:

[
 {
    "price": 2419.62,
    "amount": 0.0266
  },
  {
    "price": 1927.52,
    "amount": 0.0217
  },
  ...
]

I tried different options. At the moment this option is the fastest:

      const points = [
           {
              "price": 2419.62,
              "amount": 0.0266
            },
            {
              "price": 1927.52,
              "amount": 0.0217
            },
            ...
          ];
      const range = 500;
      const spread = 1800;
      const countGroup = 250;
      const sizeUnitGroup = range / countGroup;
      const groups = {};
      for (let i = 0;  i < countGroup; i++){
        groups[i] = [];
        try {
          points.forEach((item, id) => {
            if (item.price > spread + (i*sizeUnitGroup) && item.price <= spread + (i*sizeUnitGroup + sizeUnitGroup)){
              groups[i].push(item);
              points.splice(id, 1);
            }
            if (item.price > (spread + (i*sizeUnitGroup + sizeUnitGroup))) throw BreakException;
          });
        } catch (e) {
        }
      }

But even so, this function works for too long. Any ideas how this can be optimized?

Please post an example update for your example array (how are things regrouped?). — kabanus
– kabanus, Commented Feb 24, 2018 at 16:00
That's a lot of iterating and splicing. Wouldn't it be better to just iterate the points array and figure out which group each one should go into? — user9366559
– user9366559, Commented Feb 24, 2018 at 16:01
Yes, did that help? It avoids the .splice(), which has to reindex the array every time. — user9366559
– user9366559, Commented Feb 24, 2018 at 16:11

Nina Scholz · Accepted Answer · 2018-02-24 18:07:25Z

3

You could calculate the interval for pushing the value to the wanted slot.

var points = [
        { price: 2419.62, amount: 0.0266 },
        { price: 1927.52, amount: 0.0217 },
        { price: 1800, amount: 0.07 },              // -1 not in result
        { price: 1800.000000000001, amount: 0.07 }, //  0
        { price: 1802, amount: 0.07 },              //  0
    ],
    range = 500,
    spread = 1800,
    countGroup = 250,
    sizeUnitGroup = range / countGroup,
    groups = {};

points.forEach((item, id) => {
    var i = Math.ceil((item.price - spread- sizeUnitGroup) / sizeUnitGroup);
    if (i >= 0 && i < countGroup) {
        groups[i] = groups[i] || [];
        groups[i].push(item);
    }
});

console.log(groups);

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Feb 24, 2018 at 18:07

Nina Scholz

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