DataCollator.java

package datacollator;

import java.util.List;
import java.util.ArrayList;
import java.awt.geom.Point2D;
import java.io.File;
import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.awt.Image;
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;

public class DataCollator {
	public static Graph readGraph(File f){
		String title = "",xLabel = "",yLabel = "";
		List<Point2D> points = new ArrayList<>();
		try(BufferedReader read = new BufferedReader(new FileReader(f));){
			String line = read.readLine();
			String[] labels = line.split(":");
			title = labels[1];
			xLabel =labels[2];
			yLabel = labels[3];
			while((line = read.readLine()) != null){
				String[] xyParts = line.split(":");
				points.add(new Point2D.Double(Double.parseDouble(xyParts[0]),Double.parseDouble(xyParts[1])));
			}
		} catch (IOException ignored){
			System.out.println(ignored);
		}
		return new Graph(title,xLabel,yLabel,points);
	}
	
	public static void main(String[] args){
		File dataFile = new File(args[0]);
		Graph graphedData = readGraph(dataFile);
		BufferedImage graphImage = graphedData.drawSelf(500,500);
		try{
			ImageIO.write(graphImage,"bmp",new File(graphedData.graphTitle + ".bmp"));
		} catch (IOException ignored){
			System.out.println(ignored);
		}
	}
}

Graph.java

import java.util.List;
import java.awt.geom.Point2D;
import java.util.Comparator;
import java.util.Collections;
import java.awt.Image;
import java.awt.image.BufferedImage;
import java.awt.Graphics;
import java.awt.Color;

public class Graph{
	private static Comparator<Point2D>  xValueComparator = new Comparator<Point2D>() {
		@Override 
		public int compare(Point2D p1, Point2D p2){
			return p1.getX() > p2.getX()? 1: p2.getX()>p1.getX()? -1:0;
		}
	};
	
	private static Comparator<Point2D>  yValueComparator = new Comparator<Point2D>() {
		@Override 
		public int compare(Point2D p1, Point2D p2){
			return p1.getY() > p2.getY()? 1: p2.getY()>p1.getY()? -1:0;
		}
	}
	;
	public static class Line {
		public final double slope,xIntercept;
		public Line(double slope, double xIntercept){
			this.slope=slope;
			this.xIntercept =xIntercept;
		}
		
		@Override
		public String toString(){
			return String.format("y=%.3f+%.3f",slope,xIntercept);
		}
		
		public static Line lineBetween(Point2D p1, Point2D p2){
			double m = (p1.getY()-p2.getY())/(p1.getX()-p2.getX());
			double b = p1.getY()- m*p1.getX();
			return new Line(m,b);
		}
	}

	public final String graphTitle;
	public final String xLabel,yLabel;
	public final List<Point2D> dataPoints;
	
	public Graph(String title, String xLbl, String yLbl, List<Point2D> points){	
		graphTitle = title;
		xLabel=xLbl;
		yLabel=yLbl;
		dataPoints=points;
	}
	
	
	public Point2D minimumXPoint(){
		return Collections.min(dataPoints,xValueComparator);
	}
	
	public Point2D minimumYPoint(){
		return Collections.min(dataPoints,yValueComparator);
	}
	
	public Point2D maximumXPoint(){
		return Collections.max(dataPoints,xValueComparator);
	}
	
	public Point2D maximumYPoint(){
		return Collections.max(dataPoints,yValueComparator);
	}
	
	public Line lineOfBestFit(){
		double m=0;
		double b=0;
		Point2D atIndex0 = dataPoints.get(0);
		for(int i=1; i< dataPoints.size()-1;i++){
			Line l = Line.lineBetween(atIndex0,dataPoints.get(i));
			m+=l.slope;
			b+=l.xIntercept;
		}
		m/=dataPoints.size()-1;
		b/=dataPoints.size()-1;
		return new Line(m,b);
	}
	
	public BufferedImage drawSelf(int width, int height){
		BufferedImage graphImage = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		
		Graphics g = graphImage.createGraphics();
		
		double maxX = maximumXPoint().getX();
		double minX = minimumXPoint().getX();
		double maxY = maximumYPoint().getY();
		double minY = minimumYPoint().getY();
		double xScale = width/(maxX-minX);
		double yScale = height/(maxY-minY);
		
		g.drawString(graphTitle,width/2-3*graphTitle.length(),10);
		g.drawString(xLabel,width/2-3*xLabel.length(),height);
		for(int i = 0; i < yLabel.length();i+=3)
			g.drawString(yLabel.substring(i,i+3),0,height/2+10*i/3);
		
		double xShift = -minX;
		double yShift = height-minY;
		
		for(Point2D p:dataPoints){
			g.fillOval((int) (xScale * (p.getX() + xShift)),(int) -((yScale * p.getY()) - yShift),5,5);
		}
		
		
		Line bestFit = lineOfBestFit();
		int bestFitStartX = (int) (xScale * ((minY-bestFit.xIntercept)/bestFit.slope + xShift));
		int bestFitStartY = (int) -((yScale * (bestFit.slope*minX+bestFit.xIntercept)) - yShift);
		int bestFitEndX = (int) (xScale * ((maxY-bestFit.xIntercept)/bestFit.slope + xShift));
		int bestFitEndY = (int) -((yScale * (bestFit.slope*maxX+bestFit.xIntercept)) - yShift);
		
		g.setColor(Color.GREEN);

		g.drawLine(bestFitStartX,bestFitStartY,bestFitEndX,bestFitEndY);
		
		return graphImage;
		
	}
		
}