Java 绘制正弦和余弦函数
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Plot the sine and cosine functions
提问by Khilmarsen
I'm currently having some problems regarding my homework.
我目前在家庭作业方面遇到了一些问题。
Here's the Exercise:
这是练习：
(Plot the sine and cosine functions) Write a program that plots the sine function in red and the cosine function in blue.
hint:The Unicode for Pi is \u03c0. To display -2Pi, use g.drawString("-2\u03c0", x, y). For a trigonometric function like sin(x), x is in radians. Use the following loop to add the points to a polygon p
（绘制正弦和余弦函数）编写一个程序，以红色绘制正弦函数，以蓝色绘制余弦函数。
提示：Pi 的 Unicode 是\u03c0。要显示 -2Pi，请使用 g.drawString("-2\u03c0", x, y)。对于像 sin(x) 这样的三角函数，x 的单位是弧度。使用以下循环将点添加到多边形p
for (int x = -170; x <= 170; x++) {
p.addPoint(x + 200, 100 - (int)(50 * Math.sin((x / 100.0) * 2 * Math.PI)));
-2Pi is at (100, 100), the center of the axis is at (200, 100), and 2Pi is at (300, 100) Use the drawPolyline method in the Graphicsclass to connect the points.
-2Pi 在 ( 100, 100) 处，轴心在 ( 200, 100) 处，2Pi 在 ( 300, 100) 使用Graphics类中的 drawPolyline 方法连接点。
Okay, so the sin function I have is a little different from the one in the exercise but it works so it shouldn't be a problem. The cosine function on the other hand, I'm having trouble finding the code for it so I don't have that in my program.
好的，所以我拥有的 sin 函数与练习中的函数略有不同，但它有效，所以应该没有问题。另一方面，余弦函数，我找不到它的代码，所以我的程序中没有它。
What I also need to do is place -Pi and Pi on the graph on their respectable places.
我还需要做的是将 -Pi 和 Pi 放在图上它们值得尊敬的位置。
So, here's the code.
所以，这是代码。
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Polygon;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Exercise13_12 extends JFrame {
public Exercise13_12() {
setLayout(new BorderLayout());
add(new DrawSine(), BorderLayout.CENTER);
}
public static void main(String[] args) {
Exercise13_12 frame = new Exercise13_12();
frame.setSize(400, 300);
frame.setTitle("Exercise13_12");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
class DrawSine extends JPanel {
double f(double x) {
return Math.sin(x);
}
double g(double y) {
return Math.cos(y);
}
protected void paintComponent(Graphics g) {
super.paintComponent(g);
g.drawLine(10, 100, 380, 100);
g.drawLine(200, 30, 200, 190);
g.drawLine(380, 100, 370, 90);
g.drawLine(380, 100, 370, 110);
g.drawLine(200, 30, 190, 40);
g.drawLine(200, 30, 210, 40);
g.drawString("X", 360, 80);
g.drawString("Y", 220, 40);
Polygon p = new Polygon();
for (int x = -170; x <= 170; x++) {
p.addPoint(x + 200, 100 - (int) (50 * f((x / 100.0) * 2
* Math.PI)));
}
g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
g.drawString("-2\u03c0", 95, 115);
g.drawString("2\u03c0", 305, 115);
g.drawString("0", 200, 115);
}
}
}
If anyone have the time to help me out I would be very grateful.
如果有人有时间帮助我，我将不胜感激。
采纳答案by Hanlet Esca?o
Try this:
尝试这个：
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Exercise13_12 extends JFrame {
public Exercise13_12() {
setLayout(new BorderLayout());
add(new DrawSine(), BorderLayout.CENTER);
}
public static void main(String[] args) {
Exercise13_12 frame = new Exercise13_12();
frame.setSize(400, 300);
frame.setTitle("Exercise13_12");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
class DrawSine extends JPanel {
double f(double x) {
return Math.sin(x);
}
double gCos(double y) {
return Math.cos(y);
}
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
g.drawLine(10, 100, 380, 100);
g.drawLine(200, 30, 200, 190);
g.drawLine(380, 100, 370, 90);
g.drawLine(380, 100, 370, 110);
g.drawLine(200, 30, 190, 40);
g.drawLine(200, 30, 210, 40);
g.drawString("X", 360, 80);
g.drawString("Y", 220, 40);
Polygon p = new Polygon();
Polygon p2 = new Polygon();
for (int x = -170; x <= 170; x++) {
p.addPoint(x + 200, 100 - (int) (50 * f((x / 100.0) * 2
* Math.PI)));
}
for (int x = -170; x <= 170; x++) {
p2.addPoint(x + 200, 100 - (int) (50 * gCos((x / 100.0) * 2
* Math.PI)));
}
g.setColor(Color.red);
g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
g.drawString("-2\u03c0", 95, 115);
g.drawString("2\u03c0", 305, 115);
g.drawString("0", 200, 115);
g.setColor(Color.blue);
g.drawPolyline(p2.xpoints, p2.ypoints, p2.npoints);
}
}
}
Basically it's the same code all over, but you need a new polygon to draw it. And then I set the color using the setColor() function of the Graphics.
基本上都是一样的代码，但是你需要一个新的多边形来绘制它。然后我使用 Graphics 的 setColor() 函数设置颜色。
回答by j2e
You can add this to your paintComponentmethod:
您可以将其添加到您的paintComponent方法中：
//Draw pi and -pi
g.drawString("-\u03c0", 147, 100);
g.drawString("\u03c0", 253, 100);
//Create a new polygon
Polygon p2 = new Polygon();
//Add the points of the cosine
for (int x = -170; x <= 170; x++) {
p2.addPoint(x + 200, 100 - (int) (50 * g((x / 100.0) * 2
* Math.PI)));
}
//Draw the function
g.drawPolyline(p2.xpoints, p2.ypoints, p2.npoints);
With that you can have the results that you need.
有了它，您就可以获得所需的结果。
回答by Khilmarsen
Okay so now that the program is complete i ended up with this.
好的，现在程序完成了，我最终得到了这个。
import java.awt.BorderLayout;
import java.awt.Graphics;
import java.awt.Polygon;
import java.awt.Color;
import javax.swing.JFrame;
import javax.swing.JPanel;
public class Exercise13_12 extends JFrame {
public Exercise13_12() {
setLayout(new BorderLayout());
add(new DrawSine(), BorderLayout.CENTER);
}
public static void main(String[] args) {
Exercise13_12 frame = new Exercise13_12();
frame.setSize(400, 300);
frame.setTitle("Exercise13_12");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
class DrawSine extends JPanel {
double f(double x) {
return Math.sin(x);
}
double gCos(double y) {
return Math.cos(y);
}
protected void paintComponent(Graphics g)
{
super.paintComponent(g);
g.drawLine(10, 100, 380, 100);
g.drawLine(200, 30, 200, 190);
g.drawLine(380, 100, 370, 90);
g.drawLine(380, 100, 370, 110);
g.drawLine(200, 30, 190, 40);
g.drawLine(200, 30, 210, 40);
g.drawString("X", 360, 80);
g.drawString("Y", 220, 40);
Polygon p = new Polygon();
Polygon p2 = new Polygon();
for (int x = -170; x <= 170; x++) {
p.addPoint(x + 200, 100 - (int) (50 * f((x / 100.0) * 2
* Math.PI)));
}
for (int x = -170; x <= 170; x++) {
p2.addPoint(x + 200, 100 - (int) (50 * gCos((x / 100.0) * 2
* Math.PI)));
}
g.setColor(Color.red);
g.drawPolyline(p.xpoints, p.ypoints, p.npoints);
g.drawString("-2\u03c0", 95, 115);
g.drawString("-\u03c0", 147, 115);
g.drawString("\u03c0", 253, 115);
g.drawString("2\u03c0", 305, 115);
g.drawString("0", 200, 115);
g.setColor(Color.blue);
g.drawPolyline(p2.xpoints, p2.ypoints, p2.npoints);
}
}
}
For anyone that might have the same problem as me later on.
对于以后可能和我有同样问题的任何人。
And thanks guys for helping me out, always grateful.
并感谢帮助我的人，总是心存感激。
回答by Don
check it out .....
一探究竟 .....
public class GuiBasicstest {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic herei
guiBasics gb = new guiBasics();
JFrame jf = new JFrame();
jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
jf.setSize(500,500);
jf.add(gb);
jf.setVisible(true);
}
}
................................................................................
package guibasics;
import java.awt.Graphics;
import javax.swing.JPanel;
/**
*
* @author ALI
*/
public class guiBasics extends JPanel{
//Graphics g = null;
public void paintComponent(Graphics g){
//super.paintComponent(g);
for(double i = 0; i<200;i++){
double y= Math.sin(i);
draw(i,y,g);
}
}
private void draw(double x , double y,Graphics g ){
double x1, y1;
x+=10;
y+=10;
x*=10;
y*=30;
x1=x+1;
y1=y+1;
Double d = new Double(x);
int a = d.intValue();
int b = (new Double(y)).intValue();
int c = (new Double(x1)).intValue();
int e = (new Double(y1)).intValue();
g.drawLine(a, b, c, e);
}
}
