export class filter {
    // Gets the median of a list of numbers
    private median(...arr: number[]): number {
        if (arr.length == 1) return arr[0];
        arr = arr.sort();

        if (arr.length % 2 == 0) {
            return (arr[(arr.length / 2) - 1] + arr[arr.length / 2]) / 2;
        } else {
            return arr[(arr.length - 1) / 2]
        };
    }

    // Gets the MAD of a list of numbers
    private medianAbsoluteDeviation(...arr: number[]): number {
        if (arr.length == 1) return 0;
        let med = this.median(...arr);

        return this.median(...arr.map(x => Math.abs(med - x)));
    }

    // Removes values that are greater than threshold times different from the MAD
    private removeNoise(arr: number[], threshold: number): number[] {
        let med = this.median(...arr);
        let mad = this.medianAbsoluteDeviation(...arr);

        return arr.filter(x => Math.abs(med - x) <= (threshold * mad));
    }

    // Returns the mean of a list of numbers,
    // filtering outliers that are greater than threshold times different from the list's MAD
    public filteredMean(arr: number[], threshold: number): number {
        let filtered = this.removeNoise(arr, threshold);
        return filtered.reduce((agg, x) => agg + x, 0) / arr.length;
    }
}