How do I match numbers and create 2-dimensional array?

user_10765416 0
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I have an array like so [1.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 4.6, 4.7]

How can I turn it into a 2-dimensional array that's based on matching numbers before the decimal?

ex.[[1.2, 1.3, 1.4], [2.2, 2.3], [3.0], [4.3, 4.4, 4.5, 4.6, 4.7]]

multidimensional-array arrays javascript
4 Answers

You can use Array.reduce to do this, building an array using indexes based on the integer portion of each value:

arr = [1.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 4.6, 4.7];

let res = arr.reduce((c, v) => {
  i = Math.trunc(v) - 1;
  c[i] = c[i] || [];
  c[i].push(v);
  return c;
}, []);

console.log(res);

If you could have values starting at 0, or gaps in the values, you can use a similar piece of code and then use Object.values() to just extract the filled in arrays:

arr = [0.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 6.6, 8.7];

res = arr.reduce((c, v) => {
  i = Math.trunc(v);
  c[i] = c[i] || [];
  c[i].push(v);
  return c;
}, []);
res = Object.values(res)
console.log(res);

user_94737640

Assuming you want empty arrays in between, you can use reduce() like this:

const numbers = [1.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 4.6, 4.7];

const grouped = numbers.reduce(
    (result, number) => {
        result[Math.trunc(number)].push(number);
        return result;
    },
    Array(Math.trunc(Math.max(...numbers)) + 1).fill().map(() => [])
);

Result:

[
    [],
    [1.2,1.3,1.4],
    [2.2,2.3],
    [3],
    [4.3,4.4,4.5,4.6,4.7]
]
user_44037320

Since it's always sorted, you can use this imperative approach:

const arr = [1.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 4.6, 4.7];

let curr = -Infinity;
let currArr = null;
const res = [];

for (let n of arr) {
  if (Math.trunc(n) > curr) {
    res.push(currArr = [curr = n]);
  } else {
    currArr.push(n);
  }
}

console.log(res);

It just tracks the latest number, and its current sub-array. If the next integer is greater than the current number, it creates a new array, otherwise it pushes into the current sub-array.

Some may not like using the result of an assignment as a value. If not, it can easily be reworked with a couple extra lines of code.

Admin1

use sort, then traverse using forEach and group based on Math.floor value.

const split = (data) => {
  const output = [];
  let temp = [];
  data
    .sort((a, b) => a - b)
    .forEach((num) => {
      const [first] = temp;
      if (first && Math.floor(num) > Math.floor(first)) {
        output.push([...temp]);
        temp = [];
      }
      temp.push(num);
    });
  if (temp.length > 0) {
    output.push([...temp]);
  }
  return output;
};

const data = [1.2, 1.3, 1.4, 2.2, 2.3, 3.0, 4.3, 4.4, 4.5, 4.6, 4.7];

console.log(split(data));

user_78994770
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