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

Question

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]]

Answer 1

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);

Answer 2

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]
]

Answer 3

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.

Answer 4

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));