package ac.essex.graphing.plotting; 
 
import ac.essex.graphing.plotting.Plotter; 
import ac.essex.graphing.plotting.Graph; 
 
import java.awt.*; 
 
/** 
 * 
 * Graphable Function 
 * Basic interface allowing mathematical functions to talk to the Graph renderer. 
 * 
 * <p> 
 * This program is free software; you can redistribute it and/or 
 * modify it under the terms of the GNU General Public License 
 * as published by the Free Software Foundation; either version 2 
 * of the License, or (at your option) any later version, 
 * provided that any use properly credits the author. 
 * This program is distributed in the hope that it will be useful, 
 * but WITHOUT ANY WARRANTY; without even the implied warranty of 
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 
 * GNU General Public License for more details at http://www.gnu.org 
 * </p> 
 * 
 @author Olly Oechsle, University of Essex 
 @version 1.0 
*/ 
public abstract class ContinuousFunctionPlotter extends Plotter { 
 
    public abstract double getY(double x); 
 
    public void plot(Graph graph, Graphics g, int chartWidth, int chartHeight) { 
 
        /** 
         * Record the last two points. Plotting works by drawing lines between consecutive points 
         * This ensures there are no gaps. 
         */ 
        double prevX = 0, prevY = 0; 
 
        /** 
         * Flag to make sure the first point is not drawn (there is not previous point to connect the dots to) 
         */ 
        boolean first = true; 
 
        double xRange = graph.plotSettings.getRangeX(); 
 
        /** 
         * Plot for every pixel going across the chart 
         */ 
        for (int ax = 0; ax < chartWidth; ax++) { 
 
            // figure out what X is 
            double x = graph.plotSettings.getMinX() + ((ax / (double) chartWidth) * xRange); 
 
            /** 
             * For this value of X, get the value of Y (via the abstract method) 
             */ 
            double y = getY(x); 
 
            /** 
             * Draw a line between two points 
             */ 
            if (!first && y <= graph.plotSettings.getMaxY() && y >= graph.plotSettings.getMinY()) graph.drawLine(g, prevX, prevY, x, y); 
 
            /** 
             * Remember the last two values 
             */ 
            prevX = x; 
            prevY = y; 
 
            /** 
             * To stop the first point being drawn 
             */ 
            first = false; 
 
        } 
 
    } 
 
}