Is there a function in java to get moving average

Question

I have a situation where I need to process 5000 samples from a device in every 0.5 sec.

Lets say the window size is 100, then there would be 50 points resulting fro

Answer 1

Here's one way.

public class Rolling {

    private int size;
    private double total = 0d;
    private int index = 0;
    private double samples[];

    public Rolling(int size) {
        this.size = size;
        samples = new double[size];
        for (int i = 0; i < size; i++) samples[i] = 0d;
    }

    public void add(double x) {
        total -= samples[index];
        samples[index] = x;
        total += x;
        if (++index == size) index = 0; // cheaper than modulus
    }

    public double getAverage() {
        return total / size;
    }   
}

---

public class RollingTest extends TestCase {

    private final static int SIZE = 5;
    private static final double FULL_SUM = 12.5d;

    private Rolling r;

    public void setUp() {
        r = new Rolling(SIZE);
    }

    public void testInitial() {
        assertEquals(0d, r.getAverage());
    }

    public void testOne() {
        r.add(3.5d);
        assertEquals(3.5d / SIZE, r.getAverage());
    }

    public void testFillBuffer() {
        fillBufferAndTest();
    }

    public void testForceOverWrite() {
        fillBufferAndTest();

        double newVal = SIZE + .5d;
        r.add(newVal);
        // get the 'full sum' from fillBufferAndTest(), add the value we just added,
        // and subtract off the value we anticipate overwriting.
        assertEquals((FULL_SUM + newVal - .5d) / SIZE, r.getAverage());
    }

    public void testManyValues() {
        for (int i = 0; i < 1003; i++) r.add((double) i);
        fillBufferAndTest();
    }


    private void fillBufferAndTest() {
        // Don't write a zero value so we don't confuse an initialized
        // buffer element with a data element.
        for (int i = 0; i < SIZE; i++) r.add(i + .5d);
        assertEquals(FULL_SUM / SIZE, r.getAverage());
    }
}