javascript : extrapolate an array of numbers

Question

I have to plot a graph based on the data values v/s time {x-axis= time[] ,y-axis = data1[]}. I want to extrapolate this array and then plot the graph . I used the following code is this the correct way to do so?

    function interpolateArray(data, fitCount) {

    var linearInterpolate = function (before, after, atPoint) {
        return before + (after - before) * atPoint;
    };

    var newData = new Array();
    var springFactor = new Number((data.length - 1) / (fitCount - 1));
    newData[0] = data[0]; // for new allocation
    for ( var i = 1; i < fitCount - 1; i++) {
        var tmp = i * springFactor;
        var before = new Number(Math.floor(tmp)).toFixed();
        var after = new Number(Math.ceil(tmp)).toFixed();
        var atPoint = tmp - before;
        newData[i] = linearInterpolate(data[before], data[after], atPoint);
    }
    newData[fitCount - 1] = data[data.length - 1]; // for new allocation
    return newData;
};

data1 = interpolateArray(data1,(data1.length*2))

data2 = interpolateArray(data2,(data2.length*2))

and then I converted date in epoch time and then did the same and converted back to utc time , like this

Timestamp11=interpolateArray(Timestamp11,(Timestamp11.length*2))


for(var i=0;i<Timestamp11.length;i++)
{
console.log(Timestamp11[i]);
var edgeTime11=Timestamp11[i]/1000000
var myDate11 = new Date(Time11)


var utcString = myDate11.toString();
var time = utcString.slice(16, 24);

Timestamp11[i] = time;}

window.myLine3 = new Chart(ctx3, charInit3(data1, data2, Timestamp11));

Is it the correct way to extrapolate a time series data?? if not please correct me.

for function() linearInterpolate Make sure you verify the inputs otherwise it will fail, unless, the inputs are always sanitized. And as for the empty array newData[0] = data[0]; Do an empty array and array.push... it would clean out the code. — Sergio Rodriguez, Jun 07 '21 at 08:15
but it is working very well here [link](http://jsfiddle.net/sbv2jj9m/4/) — minu, Jun 07 '21 at 08:32
If the goal is to make it work, instead of improving the code... Then yes. Even bad code runs and gets the job done. — Sergio Rodriguez, Jun 07 '21 at 10:40
If this is a math question. This is the wrong place. That said, find a method and apply the formula in code. https://en.wikipedia.org/wiki/Extrapolation — Sergio Rodriguez, Jun 07 '21 at 20:10

score 0 · Answer 1 · answered Jun 07 '21 at 12:26

Top section

 const interpolateArray = (data, fitCount) => {
  let newData = [];
  let springFactor = Number((data.length - 1) / (fitCount - 1));
  let linearInterpolate = (before, after, atPoint) => {
    return before + (after - before) * atPoint;
  };

  for (var i = 0; i < fitCount - 1; i++) {
    let tmp = i * springFactor;
    let before = Number(Math.floor(tmp)).toFixed();
    let after = Number(Math.ceil(tmp)).toFixed();
    let atPoint = tmp - before;
    newData.push(linearInterpolate(data[before], data[after], atPoint));
  }
  
  // for new allocation
  newData[fitCount - 1] = data[data.length - 1];
  
  return newData;
};

let originalArry = [1, 5, 3];
let newArry = interpolateArray([1, 5, 3], 5);
let p1 = document.createElement('div');
let p2 = document.createElement('div');
document.body.appendChild(p1);
document.body.appendChild(p2);
p1.textContent = 'Original Array : ' + JSON.stringify(originalArry);
p2.textContent = 'After Intrapolation( value = 5) : ' + JSON.stringify(newArry);

javascript : extrapolate an array of numbers

1 Answers1