[removed] remove outlier from an array?

Question

values = [8160,8160,6160,22684,0,0,60720,1380,1380,57128]

how can I remove outliers like 0, 57218, 60720 and 22684?

Is there a library whic

Answer 1

This is an improved version of @james-peterson solution that updates the syntax to the current Javascript standard and adds a more robust way of finding the two quartiles (implemented according to formulas at https://de.wikipedia.org/wiki/Interquartilsabstand_(Deskriptive_Statistik) ). It uses a faster way of copying the array (see http://jsben.ch/wQ9RU for a performance comparison) and still works for q1 = q3.

function filterOutliers(someArray) {

  if(someArray.length < 4)
    return someArray;

  let values, q1, q3, iqr, maxValue, minValue;

  values = someArray.slice().sort( (a, b) => a - b);//copy array fast and sort

  if((values.length / 4) % 1 === 0){//find quartiles
    q1 = 1/2 * (values[(values.length / 4)] + values[(values.length / 4) + 1]);
    q3 = 1/2 * (values[(values.length * (3 / 4))] + values[(values.length * (3 / 4)) + 1]);
  } else {
    q1 = values[Math.floor(values.length / 4 + 1)];
    q3 = values[Math.ceil(values.length * (3 / 4) + 1)];
  }

  iqr = q3 - q1;
  maxValue = q3 + iqr * 1.5;
  minValue = q1 - iqr * 1.5;

  return values.filter((x) => (x >= minValue) && (x <= maxValue));
}

See this gist: https://gist.github.com/rmeissn/f5b42fb3e1386a46f60304a57b6d215a