1. Functions that Deal with Arrays CS 1111 Ryan Layer Feb 23, 2010

2. Plotting a Function Graph

3. Sampling y=sin(4x) + sin(20x)
public class PlotFunction {
// Plot y = sin(4x) + sin(20x)
public static void main(String[] args) {
int N = Integer.parseInt(args[0]);
double[] a = new double[N+1];
for (int i = 0; i <= N; i++)
a[i] = Math.sin(4*Math.PI*i/N)
+ Math.sin(20*Math.PI*i/N);
StdDraw.setXscale(0, N);
StdDraw.setYscale(-2.0,2.0);
for (int i = 1; i <= N; i++)
StdDraw.line(i-1, a[i-1], i , a[i]);
//StdDraw.save("sine.png"); } 5 20
200

4. Random Numbers import java.awt.Color; 500
int N = Integer.parseInt(args[0]);
double scale = 1.0/N;
double[] rands = new double[N];
StdDraw.setPenRadius(0.005);
for (int i = 0; i < N; i++) {
rands[i] = Math.random();
StdDraw.point(i*scale, rands[i]); }
StdDraw.setPenRadius(0.01);
StdDraw.setPenColor(new Color(255,0,0));
double sum = 0;
sum += rands[i];
StdDraw.point(i*scale, sum/i);
//StdDraw.save("rand.png");
500

5. Sound
C:523.25
B:493.88
A:440.0
G:391.59
sin(2пt × f)
F:348.50

6. Sampling Sound Hz:440 int sps = Integer.parseInt(args[0]);
double hz = Double.parseDouble(args[1]);
double duration = 1.0/40.0;
int N = (int) (sps * duration);
double[] a = new double[N+1];
for (int i = 0; i <= N; i++)
a[i] = Math.sin(2*Math.PI*i*hz/sps);
StdDraw.setXscale(0, N);
StdDraw.setYscale(1.1,-1.1);
for (int i = 1; i <= N; i++)
StdDraw.point(i , a[i]);
StdDraw.setPenRadius(0.002);
StdDraw.line(i-1, a[i-1], i , a[i]);
5512
11025
44100

7. Sampling Sound Hz:440 int sps = Integer.parseInt(args[0]);
double hz = Double.parseDouble(args[1]);
double duration = 1.0/40.0;
int N = (int) (sps * duration);
double[] a = new double[N+1];
for (int i = 0; i <= N; i++)
a[i] = Math.sin(2*Math.PI*i*hz/sps);
StdAudio.play(a);
5512
11025
44100

8. Notes = Songs A A B C A A B C A int sps = Integer.parseInt(args[0]);
double[] notes = {440.0, , , 440.0};
double duration = 0.5;
int N = (int) (sps * duration);
double[] a = new double[2*notes.length*(N+1)];
for (int i = 0; i < 2; i++) {
for (int j = 0; j < notes.length; j++) {
for (int k = 0; k < N; k++) {
int c = i * notes.length*N + j*N + k;
a[c] = Math.sin(2*Math.PI* c*notes[j]/sps); }
StdAudio.play(a); A
N samples per note A B C A A B C A
4 notes

9. Array Input/Output //double[] notes = {440.0, 493.88, 523.25, 440.0};
int sps = Integer.parseInt(args[0]);
double[] notes = {440.0, , , 440.0};
double duration = 0.5;
int N = (int) (sps * duration);
double[] a = new double[2*notes.length*(N+1)];
for (int i = 0; i < 2; i++) {
for (int j = 0; j < notes.length; j++) {
for (int k = 0; k < N; k++) {
int c = i * notes.length*N + j*N + k;
a[c] = Math.sin(2*Math.PI* c*notes[j]/sps); }
StdAudio.play(a);
//double[] notes = {440.0, , , 440.0};
double[] notes = StdArrayIO.readDouble1D();

10. Arrays as Arguments public static void plotPoints(double[] a) {
int N = a.length;
StdDraw.setXscale(0, N-1);
StdDraw.setPenRadius(1.0 / (3.0 * N));
for (int i = 0; i < N; i++) {
StdDraw.point(i, a[i]); }
public static void plotLines(double[] a) {
StdDraw.setPenRadius();
for (int i = 1; i < N; i++) {
StdDraw.line(i-1, a[i-1], i, a[i]);
public static void plotBars(double[] a) {
StdDraw.setPenRadius(0.5 / N);
StdDraw.line(i, 0, i, a[i]);