How to Flatten an Array of Arrays - But Not All the Way Down

How to flatten an array of arrays - but not all the way down

use flatten(1) http://apidock.com/ruby/Array/flatten

your_array = [[["Club three Team one", 7800], ["Club three Team two", 7801]], [], [["Club four Team one", 7807], ["Club four Team two", 7808]], []]
your_array.flatten(1)
#=> [["Club three Team one", 7800], ["Club three Team two", 7801], ["Club four Team one", 7807], ["Club four Team two", 7808]]

How to flatten nested array in javascript?

This is an alternative to recursion (see jsfiddle here) and should accept any level of depth which avoids stack overflow.

var array = [[0, 1], [2, 3], [4, 5, [6, 7, [8, [9, 10]]]]];console.log(flatten(array), array); // does not mutate arrayconsole.log(flatten(array, true), array); // array is now empty
// This is done in a linear time O(n) without recursion// memory complexity is O(1) or O(n) if mutable param is set to falsefunction flatten(array, mutable) {    var toString = Object.prototype.toString;    var arrayTypeStr = '[object Array]';        var result = [];    var nodes = (mutable && array) || array.slice();    var node;
    if (!array.length) {        return result;    }
    node = nodes.pop();        do {        if (toString.call(node) === arrayTypeStr) {            nodes.push.apply(nodes, node);        } else {            result.push(node);        }    } while (nodes.length && (node = nodes.pop()) !== undefined);
    result.reverse(); // we reverse result to restore the original order    return result;}

Merge/flatten an array of arrays

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ES2019

ES2019 introduced the Array.prototype.flat() method which you could use to flatten the arrays. It is compatible with most environments, although it is only available in Node.js starting with version 11, and not at all in Internet Explorer.

const arrays = [
      ["$6"],
      ["$12"],
      ["$25"],
      ["$25"],
      ["$18"],
      ["$22"],
      ["$10"]
    ];
const merge3 = arrays.flat(1); //The depth level specifying how deep a nested array structure should be flattened. Defaults to 1.
console.log(merge3);
    

Flatten array of arrays in TypeScript

Try this:

const a = [["a", "b", "c"], ["a", "b", "c"], ["a", "b", "c"]]const result = a.reduce((accumulator, value) => accumulator.concat(value), []);console.log(result)

Flattening a list of NumPy arrays?

You could use numpy.concatenate, which as the name suggests, basically concatenates all the elements of such an input list into a single NumPy array, like so -

import numpy as np
out = np.concatenate(input_list).ravel()

If you wish the final output to be a list, you can extend the solution, like so -

out = np.concatenate(input_list).ravel().tolist()

Sample run -

In [24]: input_list
Out[24]: 
[array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]]),
 array([[ 0.00353654]])]

In [25]: np.concatenate(input_list).ravel()
Out[25]: 
array([ 0.00353654,  0.00353654,  0.00353654,  0.00353654,  0.00353654,
        0.00353654,  0.00353654,  0.00353654,  0.00353654,  0.00353654,
        0.00353654,  0.00353654,  0.00353654])

Convert to list -

In [26]: np.concatenate(input_list).ravel().tolist()
Out[26]: 
[0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654,
 0.00353654]

How do I flatten an array of arrays?

In a first step, you have to normalize the data to one kind of type. Then you can iterate over them as you like. So at first create a method to flatten the values from a specific point to an arbitrary depth:

public static class Extensions
{
    public static IEnumerable<object> FlattenArrays(this IEnumerable source)
    {
        foreach (var item in source)
        {
            if (item is IEnumerable inner
                && !(item is string))
            {
                foreach (var innerItem in inner.FlattenArrays())
                {
                    yield return innerItem;
                }
            }

            yield return item;
        }
    }
}

Now you can either iterate on the top level to get a single array of all values:

// Produces one array => ["1", "2", "3", "4", ...]
var allFlat = schools.FlattenArrays().OfType<string>().ToArray();

Or you can create individual array one depth deeper:

foreach (var item in schools)
{
    // Produces an array for each top level e.g. ["5", "6", "7", "8"]
    var flat = item.FlattenArrays().OfType<string>().ToArray();
}

How to Flatten a Multidimensional Array?

You can use the Standard PHP Library (SPL) to "hide" the recursion.

$a = array(1,2,array(3,4, array(5,6,7), 8), 9);
$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($a));
foreach($it as $v) {
  echo $v, " ";
}

prints

1 2 3 4 5 6 7 8 9 

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