Find most stable point of two array parallelly

March 4, 2022

I have two arrays.

let arr1 = [32, 35, 25, 37, 40, 45, 42, 46, 44, 45, 49, 50];
let arr2 = [46, 55, 55, 56, 57, 64, 70, 71, 78, 85, 86, 97];

Now I want a "stable" index of both arrays. like what is the index when both arrays are most state?

For example from the given array I want.

let index = 8 // this is what i want

Index 8 means from arr1 the ist "44" and from arr2 "78"

Let me define what I mean by `stable` here.

At least their one before element and one after element’s difference is the least of both arrays. (Sorry for my bad explanation.)

Don’t flag this question just comment on what you need to know, I will try to explain. [Please]

As recommended by @Nina Scholz

This is what i tried so far [not working]

let arr1 = [32, 35, 25, 37, 40, 45, 42, 46, 44, 45, 49, 50];
let arr2 = [46, 55, 55, 56, 57, 64, 70, 71, 78, 85, 86, 97];
let diff_arr1 = []
let diff_arr2 = []
let compare_arr = []

for (let i = 0; i < arr1.length; i++) {
    diff_arr1.push(Math.abs(arr1[i + 1] - arr1[i]));
}

for (let i = 0; i < arr2.length; i++) {
    diff_arr2.push(Math.abs(arr2[i + 1] - arr2[i]));
}

for (let i = 0; i < 12; i++) {
    compare_arr.push(Math.abs(diff_arr2[i] - diff_arr1[i]));
}

console.log("Array 1")
console.log("Array 1 diff");
console.log(diff_arr1);

console.log("Array 2")
console.log("Array 2 diff");
console.log(diff_arr2);

console.log('compare_arr')
console.log(compare_arr)
let arr_temp = compare_arr.filter(function (value) {
    return !Number.isNaN(value);
});
console.log(Math.min.apply(Math, arr_temp));

>Solution :

You could take the delta of the previous value with actual and actual and next value and take later this delta the get a minimum delta of both deltas.

The result is different from the wanted, because it take the minimum delta of both arrays.

                          v
 32, 35, 25, 37, 40, 45, 42, 46, 44, 45, 49, 50
NaN  13  22  15   8   8   7   6   3   5   5 NaN

 46, 55, 55, 56, 57, 64, 70, 71, 78, 85, 86, 97
NaN   9   1   2   8  13   7   8  14   8  12 NaN

const
    getDelta = (array, offset) => array
        .map((v, i, a) => Math.abs(v - array[i - 1]) + Math.abs(v - array[i + 1])),
    array1 = [32, 35, 25, 37, 40, 45, 42, 46, 44, 45, 49, 50],
    array2 = [46, 55, 55, 56, 57, 64, 70, 71, 78, 85, 86, 97],
    delta1 = getDelta(array1, 2),
    delta2 = getDelta(array2, 2),
    result = [...array1.keys()]
        .slice(1, -1)
        .reduce((a, b) => Math.abs(delta1[a] - delta2[a]) < Math.abs(delta1[b] - delta2[b])
        ? a
        : b
    );

console.log(result);
console.log(...delta1.map(v => v.toString().padStart(2, ' ')));
console.log(...delta2.map(v => v.toString().padStart(2, ' ')));