How to detect outliers in an ArrayList

Question

I\'m trying to think of some code that will allow me to search through my ArrayList and detect any values outside the common range of \"good values.\"

Example: 100 1

Answer 1

An implementation of the Grubb's test can be found at MathUtil.java. It will find a single outlier, of which you can remove from your list and repeat until you've removed all outliers.

Depends on commons-math, so if you're using Gradle:

dependencies {
  compile 'org.apache.commons:commons-math:2.2'
}

Answer 2

It is just a very simple implementation which fetches the information which numbers are not in the range:

List<Integer> notInRangeNumbers = new ArrayList<Integer>();
for (Integer number : numbers) {
    if (!isInRange(number)) {
        // call with a predefined factor value, here example value = 5
        notInRangeNumbers.add(number, 5);
    }
}

Additionally inside the isInRange method you have to define what do you mean by 'good values'. Below you will find an examplary implementation.

private boolean isInRange(Integer number, int aroundFactor) {
   //TODO the implementation of the 'in range condition'
   // here the example implementation
   return number <= 100 + aroundFactor && number >= 100 - aroundFactor;
}