Increment array values evenly using javascript?

Question

I have an arrays of 5 values containing example:

I need to convert to arrays holding 100 values spaced in same proportion and containing as well the original 5 values in the sequence. Like:

[0.01,...,0.1,...1,...10,...100]

I thought I could use numeric.linspace(0.01,100,100); http://www.numericjs.com/documentation.html

But this only passes first and last wanted value. Ideally some function that accepts an array of n values as first parameter and the final wanted array.length

I was not sure how to formulate the question so please suggest a different title if more appropriated...

Can you explain using input and output? Like if I input 5 or 0.1 what should be the output? — Rajesh Dixit
– Rajesh Dixit, Commented Jan 19, 2017 at 9:50
So sorry guys does not make sense what I posted...obviously it is not possible to maintain even spaced proportions and original values in between min and max at the same time..... — Al Ex Tsm
– Al Ex Tsm, Commented Jan 19, 2017 at 10:00

Giladd · Accepted Answer · 2017-01-19 10:02:22Z

1

Hope this is what you meant:

function expand(arr, len){
  var perSection = Math.floor(len / (arr.length - 1));
  var out = [];
  var val;
  console.log('Per Section:', perSection);
  
  for (let i = 0; i < arr.length - 1; i++) {
  	val = arr[i];
    out.push(val);
    var interval = (arr[i+1] - arr[i]) / perSection;
    console.log('ival', interval);
  	for (let j = 0; j < perSection-1; j++) {
    	val += interval;
    	out.push(val)
    }
  }
  out.push(arr[arr.length-1]);
  
  return out;
}

console.log(expand([10, 40, 70, 100], 10));

Note that the length of the resulting array will not always match exactly to the requested length, as there might be rounding errors when calculating how many numbers go into each interval.
Depending on the required behavior additional logic can be added to handle these edge cases.

answered Jan 19, 2017 at 10:02

Giladd

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Comments

Nina Scholz · Accepted Answer · 2017-01-19 09:34:48Z

1

You could map the values with a weight.

var space = [0.01, 0.1, 1, 10, 100],
    value = 7,
    values = space.map(function (a, i, aa) {
        this.last = i ? this.last * a / aa[i - 1] : value;
        return this.last;
    }, { });

console.log(values);

answered Jan 19, 2017 at 9:34

Nina Scholz

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