How to add each set of numbers within an array of arrays? (javascript)

Question

I'm struggling to design a loop that will cycle through an array of arrays and add each number together, work out the average then output to the console.

Here is my code;

var data = [
  [3, 6, 14, 17, 30, 40, 44, 66, 69, 84, 92, 95],
  [100, 17, 26, 28, 29, 34, 38, 59, 78, 82, 84, 93],
  [6, 12, 22, 25, 35, 44, 45, 57, 60, 61, 78, 80],
  [6, 11, 14, 19, 33, 50, 57, 58, 61, 88, 89, 97],
  [6, 13, 23, 28, 39, 44, 50, 55, 58, 72, 80, 88],
  [6, 8, 22, 26, 48, 50, 55, 65, 77, 84, 93, 99]
]

var calcTotal, arrayTotal, totalSum;
calcTotal = [];
arrayTotal = [];
totalSum = [];
arrayTotal.push(data[0])
totalSum = data[0].reduce(function(a, b) {
  return a + b;
});
calcTotal.push(totalSum)


console.log(Math.round(totalSum / 12))

http://plnkr.co/edit/Ses4XApKEdo2CCZmsis7?p=preview

So far I have it working to display just one result, Ideally I would output the average from each array when added together in a single array to the console.

I've been playing around with for/forEach loops but can't seem to crack it, if anyone can offer some help/advice?

Thanks

function sum(a,b){return a+b;} averages = data.map(function(s){return s.reduce(sum,0)/s.length;}); globalAverage = averages.reduce(sum,0)/averages.length; - Something like that, perhaps? — Niet the Dark Absol
– Niet the Dark Absol, Commented Aug 3, 2016 at 12:35

Pavlo · Accepted Answer · 2016-08-03 12:55:45Z

1

It's pretty easy: you can write two functions, add and average, use Array#map and Array#reduce:

var data = [
  [3, 6, 14, 17, 30, 40, 44, 66, 69, 84, 92, 95],
  [100, 17, 26, 28, 29, 34, 38, 59, 78, 82, 84, 93],
  [6, 12, 22, 25, 35, 44, 45, 57, 60, 61, 78, 80],
  [6, 11, 14, 19, 33, 50, 57, 58, 61, 88, 89, 97],
  [6, 13, 23, 28, 39, 44, 50, 55, 58, 72, 80, 88],
  [6, 8, 22, 26, 48, 50, 55, 65, 77, 84, 93, 99]
];

function add(a, b) {
  return a + b;
}

function average(list) {
  return list.reduce(add) / list.length;
}

document.body.textContent = data.map(average);

edited Aug 3, 2016 at 12:55

answered Aug 3, 2016 at 12:39

Pavlo

45.2k14 gold badges83 silver badges114 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Oriol Over a year ago

Consider list.reduce(add, 0) if you want average([]) to return NaN instead of throwing an error.

Ernest Nowacki · Accepted Answer · 2016-08-03 12:35:36Z

So as far as I understand you need to display to the console average of each row right?

You've done pretty good job with single line it just needed to be packed with forEach, here's working fiddle: https://jsfiddle.net/enowacki/dhdc1ztc/2/

const data = [
  [3, 6, 14, 17, 30, 40, 44, 66, 69, 84, 92, 95],
  [100, 17, 26, 28, 29, 34, 38, 59, 78, 82, 84, 93],
  [6, 12, 22, 25, 35, 44, 45, 57, 60, 61, 78, 80],
  [6, 11, 14, 19, 33, 50, 57, 58, 61, 88, 89, 97],
  [6, 13, 23, 28, 39, 44, 50, 55, 58, 72, 80, 88],
  [6, 8, 22, 26, 48, 50, 55, 65, 77, 84, 93, 99]
];

const result = data.map((arr) => {
  const rowSum = arr.reduce((prev, curr) => prev + curr);
  const rowCount = arr.length;
  const avg = Math.round(rowSum / rowCount);
  
  return avg;
});

console.log(result);

I've extracted some additional variables so you can clearly see what's going on feel free to omit them if not needed.

msfoster · Accepted Answer · 2016-08-03 12:37:08Z

0

Flatten:

var flat = [].concat.apply([], data);

Sum:

var sum = flat.reduce((a, b) => a+b, 0);
console.log("Avg:" + Math.round(sum / flat.length);

answered Aug 3, 2016 at 12:37

msfoster

2,5721 gold badge19 silver badges19 bronze badges

Collectives™ on Stack Overflow

How to add each set of numbers within an array of arrays? (javascript)

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related