final int FRAME_RATE = 30;
final int ARRAY_SIZE = 40;
final int WIDTH = 400;
final int HEIGHT = 250;


float[] datum = new float[ARRAY_SIZE];
  
float x1 = 0;
float y1 = 0;
float x2 = 0;
float y2 = 0;
  
float xIncrement = WIDTH/(ARRAY_SIZE-1);
float value;

void setup() {
   size(WIDTH, HEIGHT);
   frameRate(FRAME_RATE);
   colorMode(RGB,255,255,255,100);
   
   for ( int i = 0; i < ARRAY_SIZE; i ++ )
   {
      datum[i] = (float) Math.random();
    }
   smooth();
}

void draw() {
   
   strokeWeight(0);
   stroke( 0 );
   
   fill(0, 50);
   rect(0, 0, width, height);
   
   strokeWeight(2);
   stroke( #FFFF00 );
 
   for (int i = 0; i < ARRAY_SIZE-1; i++) {
      x1 = i * xIncrement;
      y1 = datum[i] * HEIGHT;
      
      x2 = (i+1) * xIncrement;
      y2 = datum[i+1] * HEIGHT;
      
      line( x1, y1, x2, y2 );
    }
   
   for (int i = 0; i < ARRAY_SIZE-1; i++) {
      datum[i] = datum[i+1]; 
    }
   value = datum[ARRAY_SIZE-2] + ( (Math.random() > .5) ? 1 : -1)* (float) (Math.random() * .15);
   value = (float) Math.max( value, 0 );
   value = (float) Math.min( value, 1 );
   datum[ARRAY_SIZE-1] = value;
}