Simple DTW(Dynamic Time Wrapping) in C#

SimpleDTW.cs

//http://data-matters.blogspot.com/2008/07/simple-implementation-of-dtwdynamic.html

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections;

namespace DTW
{
    class SimpleDTW
    {
        double[] x;
        double[] y;
        double[,] distance;
        double[,] f;
        ArrayList pathX;
        ArrayList pathY;
        ArrayList distanceList;
        double sum;

        public SimpleDTW(double[] _x, double[] _y)
        {
            x = _x;
            y = _y;
            distance = new double[x.Length, y.Length];
            f = new double[x.Length+1, y.Length+1];

            for (int i = 0; i < x.Length; ++i){
                for (int j = 0; j < y.Length; ++j){
                    distance[i, j] = Math.Abs(x[i] - y[j]);
                }
            }

            for (int i = 0; i <= x.Length; ++i)
            {
                for (int j = 0; j <= y.Length; ++j)
                {
                    f[i, j] = -1.0;
                }
            }

            for (int i = 1; i <= x.Length; ++i) {
                f[i,0] = double.PositiveInfinity;
            }
            for (int j = 1; j <= y.Length; ++j) {
                f[0, j] = double.PositiveInfinity;
            }

            f[0, 0] = 0.0;
            sum = 0.0;

            pathX = new ArrayList();
            pathY = new ArrayList();
            distanceList = new ArrayList();
        }

        public ArrayList getPathX(){
            return pathX;
        }

        public ArrayList getPathY() {
            return pathY;
        }

        public double getSum(){
            return sum;
        }

        public double[,] getFMatrix() {
            return f;
        }

        public ArrayList getDistanceList() {
            return distanceList;
        }

        public void computeDTW() {
            sum = computeFBackward(x.Length, y.Length);
            //sum = computeFForward();
        }

        public double computeFForward() {
            for (int i = 1; i <= x.Length; ++i) {
                for (int j = 1; j <= y.Length; ++j) {
                    if (f[i - 1, j] <= f[i - 1, j - 1] && f[i - 1, j] <= f[i, j - 1]) {
                        f[i, j] = distance[i - 1, j - 1] + f[i - 1, j];
                    }
                    else if (f[i, j - 1] <= f[i - 1, j - 1] && f[i, j - 1] <= f[i - 1, j]) {
                        f[i, j] = distance[i - 1, j - 1] + f[i, j - 1 ];                    
                    }
                    else if (f[i - 1, j-1 ] <= f[i , j - 1] && f[i - 1, j - 1] <= f[i-1, j ]) {
                        f[i, j] = distance[i - 1, j - 1] + f[i - 1, j - 1 ];
                    }
                }
            }
            return f[x.Length, y.Length];
        }

        public double computeFBackward(int i, int j)
        {
            if (!(f[i, j] < 0.0) ){
                return f[i, j];
            }
            else {
                if (computeFBackward(i - 1, j) <= computeFBackward(i, j - 1) && computeFBackward(i - 1, j) <= computeFBackward(i - 1, j - 1)
                    && computeFBackward(i - 1, j) < double.PositiveInfinity)
                {
                    f[i, j] = distance[i - 1, j - 1] + computeFBackward(i - 1, j);
                }
                else if (computeFBackward(i, j - 1) <= computeFBackward(i - 1, j) && computeFBackward(i, j - 1) <= computeFBackward(i - 1, j - 1)
                    && computeFBackward(i, j - 1) < double.PositiveInfinity)
                {
                    f[i, j] = distance[i - 1, j - 1] + computeFBackward(i, j - 1);    
                }
                else if (computeFBackward(i - 1, j - 1) <= computeFBackward(i - 1, j) && computeFBackward(i - 1, j - 1) <= computeFBackward(i, j - 1)
                    && computeFBackward(i - 1, j - 1) < double.PositiveInfinity)
                {
                    f[i, j] = distance[i - 1, j - 1] + computeFBackward(i - 1, j - 1);
                }
            }
            return f[i, j];
        }


    }
}