Why is the output NaN?

January 11, 2022

I’m learning Javascript, when I want to calculate using a formula the resulting data is NaN.

I want the resulting data to be

ar = [37, 36.63, 35.68, 38.81, 37.67, 37.64, 37.64, 39.74, 40.67, 40.61];

ma = [0.00, 0.63, 3.32, 0.81, 0.33, 0.36, 2.36, 1.26, 0.33, 1.61];

Is there something wrong with my code that is making me get this answer?

var suhu = [37, 36, 39, 38, 38, 38, 40, 41, 41, 39];

var ar = []
var ma = []
var temp = 0

// AR
for (var i = 1; i < suhu.length; i++) {
  ar[0] = suhu[0]
  temp = 0.99 * suhu[i - 1] + 0.06 * ma[i - 1]
  ar.push(temp)
}

// MA
for (var j = 0; j < suhu.length; j++) {
  suhu[j] = Math.abs(suhu[j] - ar[j]);
  ma.push(suhu[j])
}

console.log(ar);
// 37, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN
console.log(ma);
// 0, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN

>Solution :

The problem is that the calculation of ar[i] depends on ma[i-1] and ma[i] depends on ar[i] so you need to calculate these in the right order in a single loop.

const suhu = [37, 36, 39, 38, 38, 38, 40, 41, 41, 39];
const ar = [];
const ma = [];

// Calucate AR and MA together
ar[0] = suhu[0]
for (var i = 0; i < suhu.length; i++) {

  if (i > 0)
    ar.push(0.99 * suhu[i - 1] + 0.06 * ma[i - 1])

  ma.push(Math.abs(suhu[i] - ar[i]));
}

console.log(ar);
// [37, 36.63, 35.6778, 38.809332, 37.66855992, 37.639886404799995,
//  37.641606815711995, 39.74150359105728, 40.66550978453656, 40.6100694129278]
console.log(ma);
// [0, 0.6300000000000026, 3.3222000000000023, 0.8093319999999977, 0.33144008000000014,
//  0.36011359520000497, 2.358393184288005, 1.2584964089427189, 0.3344902154634397, 1.6100694129277997]

.as-console-wrapper{top:0;max-height:100%!important}

The results are accurate to more than 2 decimal places and you will need that to calculate the next values correctly. You can change the precision once all the values have been calculated though.