Mindboards

Code: Select all

package com.kvols.stat;

import static java.lang.Math.sqrt;

public class Stat {
	int n;
	double sumX, sumY, sumXY, sumXX, sumYY;

	public void add(double x, double y) {
		n++;
		sumX += x;
		sumY += y;
		sumXY += x * y;
		sumXX += x * x;
		sumYY += y * y;
	}

	double getMean() {
		return sumX / n;
	}

	double standardDeviation() {
		return Math.sqrt((sumXX - sumX * sumX / n) / (n - 1));
	}

	public int getN() {
		return n;
	}

	public double getSumX() {
		return sumX;
	}

	public double getSumXX() {
		return sumXX;
	}

	public double getSumXY() {
		return sumXY;
	}

	public double getSumY() {
		return sumY;
	}
	
	public double getSumYY() {
		return sumYY;
	}

	public double getBeta() {
		return (sumXY/n - sumX * sumY/(n*n))
				/ ((sumXX / n - (sumX * sumX / (n * n))));
	}

	public double getAlpha() {
		return (sumY - getBeta() * sumX) / n;
	}

	public double getCorrelation() {
		return (n * sumXY - sumX * sumY)
				/ (sqrt(n * sumXX - sumX * sumX) * sqrt(n * sumYY - sumY * sumY));
	}

	@Override
	public String toString() {
		if(n<2)
			return "Empty stats";
		return "N=" + n + "\nb:"+(float)getBeta()+"\na:"+(float)getAlpha()+"\nC:"+(float)getCorrelation();
	}
}

Code: Select all

package com.kvols.stat;

import org.junit.Test;

import static org.junit.Assert.*;

public class StatTest {

	@Test
	public void testAddMethod() {
		Stat stat = new Stat();
		stat.add(1, 2);
		stat.add(2, 3);
		stat.add(3, 4);
		assertEquals("N", 3, stat.getN());
		assertEquals("sum x", 6, stat.getSumX(), 1e-12);
		assertEquals("sum y", 9, stat.getSumY(), 1e-12);
		assertEquals("sum x²", 14, stat.getSumXX(), 1e-12);
		assertEquals("sum xy", 20, stat.getSumXY(), 1e-12);
		assertEquals("sum y²", 29, stat.getSumYY(), 1e-12);
		System.out.println(stat);
	}

	@Test
	public void testCalculations() {
		Stat stat= new Stat();
		stat.add(5,3);
		stat.add(8,2);
		stat.add(6,9);
		stat.add(5,8);
		stat.add(3,4);
		stat.add(9,2);
		assertEquals("mean", 6, stat.getMean(), 1e-12);
		assertEquals("std.dev", 2.19089023002, stat.standardDeviation(), 1e-11);
		assertEquals("correlation", -.385704038913, stat.getCorrelation(), 1e-11);
		assertEquals("beta", -.541666666667, stat.getBeta(), 1e-11);
		assertEquals("alpha", 7.91666666667, stat.getAlpha(), 1e-11);
	}
}

Code: Select all

import lejos.nxt.ADSensorPort;
import lejos.nxt.Battery;
import lejos.nxt.Button;
import lejos.nxt.LCD;
import lejos.nxt.SensorPort;

import com.kvols.stat.Stat;

public class GVSampler {
	public static void main(String[] args) throws InterruptedException {
		Stat stat= new Stat();
		ADSensorPort gyroPort= SensorPort.S1;
		gyroPort.setType(SensorPort.POWER_9V);
		
		for(;;) {
			LCD.clear();
			LCD.drawString(stat.toString(), 0, 0);
			int key= Button.readButtons();
			while(key == 0) {
				LCD.drawString("Gyro:"+gyroPort.readValue(), 0, 6);
				LCD.drawString("Batt:"+Battery.getVoltageMilliVolt(), 0, 7);
				Thread.sleep(50);
				key= Button.readButtons();
			}
			if(key==Button.ID_ENTER) {
				LCD.clear();
				LCD.drawString("Sampling...", 0, 3);
				for(int i=0; i<100; i++) {
					double batt= Battery.getVoltage();
					double gyro= gyroPort.readValue();
					batt= (Battery.getVoltage()+batt)/2;
					stat.add(batt, gyro);
					Thread.sleep(10);
				}
			}
			if(key==Button.ID_ESCAPE) break;
		}
	}
}

Code: Select all

offset= 597.2054f + Battery.getVoltage() * 1.111321f