Getting the sum of array

Question

I have an array of number [350000, 350000, 350000]

I have the following code:

function getNPV(rate, periods, Cashflow) {
    var npv = 0;
    for (var i = 0; i < Cashflow.length; i++) {
        npv += Cashflow[i] / Math.pow(1 + rate, periods);
    }
    return npv;
}

Here, cashflow is our array, rate = 6% and period = 91days.

When I take :

 npv = Cashflow[i] / Math.pow(1 + rate, periods);

The output is [348328,346664,344952] when 6% discount rate is applied to 350000 each time.

I am trying to take the sum of [348328,346664,344952] which is $1,039,944 But, it is giving me $1034856 as the result.

Trying the console, it's actually taking the sum of the 3rd value 3 times instead. [344952+344952+344952] for some reason.

Can someone please tell me how to fix this error. Any help is appreciated. Thank you.

CODE

Logic

Post your code here in the question as formatted text, not an external screenshot. — takendarkk, Oct 08 '18 at 16:36
You are not varying the period at all in your loop, all three run of the loops are using same value for period, hence same output — Aragorn, Oct 08 '18 at 16:38
There's a bug in your algorithm, not in the code. This is a mathematical problem, not a programming problem. — user247702, Oct 08 '18 at 16:40

score 0 · Accepted Answer · answered Oct 08 '18 at 16:43

0

As I refer to your spreadsheet, you need an array for period not cashflow.

Pass periods and cashflow like:

var periods = [30, 60, 91];
var cashflow = 350000;
getNPV(rate, periods, cashflow);

Your cash flow is same, so no need an array (You may still have an array if you want to vary cashflow)

And use it in the loop:

function getNPV(rate, periods, Cashflow) {
    var npv = rate;

    for (var i = 0; i < periods.length; i++) {
        npv += Cashflow / Math.pow(1 + rate, periods[i]);
    }
    return npv;
}

answered Oct 08 '18 at 16:43

Aragorn

5,021
5
26
37

Thank you. This works so far but i had to hard code it. I am not able to create and array with number of days in each month. I tried to create an array and it gives me dates in between 2 dates. But not the days. Could you give an idea on how to do this. – ace23 Oct 08 '18 at 23:52
Not sure I understand where you are struggling. An array would simply be like, `var daysInMonths = [31, 28, 30, 31, ......].` I don't think there is anything that can give you a dynamic array, you'll have to build it yourself. Try json like `{"01":"31", "02": "28", ....}` – Aragorn Oct 09 '18 at 02:26
I'd use Date object. Refer this: https://stackoverflow.com/a/315767/1205647 – Aragorn Oct 09 '18 at 14:41

score 0 · Answer 2 · answered Oct 08 '18 at 16:51

0

You can use returnSum to get the sum of the array

function returnSum(arr) {

  function sum(a, b) {
    return a + b;
  }
  return arr.reduce(sum, 0);
}

let array = [348328,346664,344952]

returnSum(array); //result 1039944

answered Oct 08 '18 at 16:51

Lenny86

120
1
9

Getting the sum of array

2 Answers2