Achieving maximum occurrence with a 2D array using JavaScript

Question

Achieving maximum occurrence with a 2D array using JavaScript

I'm trying to find the most commonly occurring string in a 2D array.

For example, given:

const arr = [['foo','bar','21'],
             ['foo', 'lar','28'],
             ['loo', 'bar','28']]

We can see that foo appears most frequently in column 1, bar in column 2, and 28 in column 3.

The size of the array may vary, so the solution needs to be dynamic.

I attempted a solution but it's complex and not suitable for multidimensional arrays:

function foo_func(array){
  if(array.length == 0)
    return null;
    var modeMap = {};
    var maxEl = array[0], maxCount = 1;
    for(var i = 0; i < array.length; i++){
      var el = array[i];
      if(modeMap[el] == null)
         modeMap[el] = 1;
   }
return maxEl;
}

If anyone has a cleaner or functional solution, I'd greatly appreciate it!

javascript arrays

Answer 1

Answer №1

To transform data into an array structure, each containing objects with keys representing properties (e.g. 'foo') and values indicating the frequency of each property in the dataset:

const arr = [
  ['foo', 'bar', '21'],
  ['foo', 'lar', '28'],
  ['loo', 'bar', '28']
];

const columns = arr.reduce((a, subarr) => {
  subarr.forEach((item, i) => {
    if (!a[i]) a[i] = {};
    a[i][item] = (a[i][item] || 0) + 1;
  });
  return a;
}, {});

const highestInEachColumnEntries = Object.values(columns).map(
  obj => Object.entries(obj)
    .reduce(
      (a, b) => a[1] > b[1] ? a : b
    )
);

const highestInEachColumnKeysOnly = highestInEachColumnEntries.map(([key]) => key);
console.log(highestInEachColumnKeysOnly);

Answer 2

To transform data into an array structure, each containing objects with keys representing properties (e.g. 'foo') and values indicating the frequency of each property in the dataset:

const arr = [
  ['foo', 'bar', '21'],
  ['foo', 'lar', '28'],
  ['loo', 'bar', '28']
];

const columns = arr.reduce((a, subarr) => {
  subarr.forEach((item, i) => {
    if (!a[i]) a[i] = {};
    a[i][item] = (a[i][item] || 0) + 1;
  });
  return a;
}, {});

const highestInEachColumnEntries = Object.values(columns).map(
  obj => Object.entries(obj)
    .reduce(
      (a, b) => a[1] > b[1] ? a : b
    )
);

const highestInEachColumnKeysOnly = highestInEachColumnEntries.map(([key]) => key);
console.log(highestInEachColumnKeysOnly);

Answer 3

Answer №2

In one approach, start by rotating the array first.

After that, you can easily identify the most common elements using reduce and filter methods.

Finally, apply the common function to the rotated array using the map method.

const arr = [
  ['foo', 'bar', '21'],
  ['foo', 'lar', '28'],
  ['loo', 'bar', '28']
];

const rotated = arr[0].map((col, i) => arr.map(row => row[i]));
const common = arr => arr.reduce((a, b, i, arr) =>
     (arr.filter(v => v === a).length >= arr.filter(v => v === b).length ? a : b));
const result = rotated.map(m => common(m));
    
console.log(result);

Answer 4

In one approach, start by rotating the array first.

After that, you can easily identify the most common elements using reduce and filter methods.

Finally, apply the common function to the rotated array using the map method.

const arr = [
  ['foo', 'bar', '21'],
  ['foo', 'lar', '28'],
  ['loo', 'bar', '28']
];

const rotated = arr[0].map((col, i) => arr.map(row => row[i]));
const common = arr => arr.reduce((a, b, i, arr) =>
     (arr.filter(v => v === a).length >= arr.filter(v => v === b).length ? a : b));
const result = rotated.map(m => common(m));
    
console.log(result);

Achieving maximum occurrence with a 2D array using JavaScript

Answer №1

Answer №2

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