将任何数字数组转换为最大值为 100 的比例值数组

Question

If I were to receive an array of numbers, how do I convert the numbers proportionally to the max value 100? For example, the acceptable range of numbers output must be between 0-100

Sorry in advance for any confusion, I am struggling to phrase the question.

Here are some examples to show what I mean:

Input Array : [7000, 500, 0, 850]

Output Array : [70, 5, 0, 8.5]

and

Input Array : [70, 550, 0, 1000]

Output Array : [7, 55, 0, 100]

and

Input Array : [7, 5, 0, 8.5]

Output Array : [70, 50, 0, 85]

To clarify: the output will only be 100 when the max value of the input array is a power of 10.

Answer 1

The term is called "normalization". I'll write in standard mathematics terminology that you can Google.

var input = [7000, 500, 0, 850]
var domainMin = Math.min.apply(Math, input)
var domainMax = Math.max.apply(Math, input)
var rangeMin = 0
var rangeMax = 100
var output = input.map(n => {
  var basis = (n - domainMin) / (domainMax - domainMin);
  return rangeMin + (rangeMax - rangeMin) * basis;
});

console.log(output);
// outputs [100, 7.142857142857143, 0, 12.142857142857142]

Now it sounds like you want to dynamically pick a different output range.

Probably, like:

var input = [7000, 500, 0, 850]
var domainMin = Math.min.apply(Math, input)
var domainMax = Math.max.apply(Math, input)
var rangeMin = domainMin && domainMin / Math.pow(10, Math.floor(Math.log10(domainMin)) - 1)
var rangeMax = domainMax / Math.pow(10, Math.floor(Math.log10(domainMax)) - 1)
console.log(rangeMin, rangeMax)
var output = input.map(n => {
  var basis = (n - domainMin) / (domainMax - domainMin);
  return rangeMin + (rangeMax - rangeMin) * basis;
});
// outputs [70, 5, 0, 8.5]

Answer 2

something like that?

 function convert2Range100 (arr) { let factor = 1, max = Math.max(...arr) if (max <= 10) factor = 0.1 while (max > 100) { factor *= 10 max /= 10 } return arr.map(v=>v/factor) } console.log(JSON.stringify( convert2Range100( [7000, 500, 0, 850]) )) console.log(JSON.stringify( convert2Range100( [70, 550, 0, 1000]) )) console.log(JSON.stringify( convert2Range100( [7, 5, 0, 8.5]) ))

Answer 3

Perhaps something as simple as this?

 const scaleTo100 = (xs) => { const factor = 100 / 10 ** (Math.ceil (Math.log10 (Math.max (...xs)))) return xs.map (x => x * factor) } console.log (scaleTo100 ([7000, 500, 0, 850])) console.log (scaleTo100 ([70, 550, 0, 1000])) console.log (scaleTo100 ([7, 5, 0, 8.5]))

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

Basically we create a factor that tells us what to multiply every input value to be finding the smallest power of 10 at least as large as every number, and then just multiply them. The factor is calculated by finding the next highest power of 10 from the maximum of our input values and dividing that into 100.

Note that this will fail if all values are zero, if that's a concern.