Linear Attractor using matrix multiplication. Click inside the square to change x or y attraction values.

matrix3.pde

// matrix.pde
// Using matrix multiplication in processingjs for an attractor

bool running = true;
int sz=250;
int dx = sz/2;
int dy = sz/2;
int sq = 20;
int counter = 1;

int[][] matrixId = {{1,0},{0,1}};
int[][] matrixA = {{round(random(width)/2),round(random(height)/2)},{round(random(width)/2),random(height)/2}};
int[][] matrixB= {{0,-0.9},{1.0,0}};
int[][] matrixC = {{0,0},{0,0}}; // new int[2][2];


void setup() {
  size(sz,sz);
  frameRate(15);
  strokeWeight(2);
  translate(dx,dy);
  text("click mouse", 0, 0);
  text(matrixA, -100, 20);
}

void setAttractorPull() {
   ++counter;

   if (abs(mouseX-dx) < sq && abs(mouseY-dy) < sq) {
//  pushMatrix();
//  translate(dx,dy);
    double ystr = (dy - mouseY) * 2 / sq;
    double xstr = (mouseX - dy) * 2 / sq;
    if (counter % 2) {
      matrixB[0][1] = xstr
      matrixB[1][0] = ystr
      // background(55);
    } else (
      matrixB[0][0] = xstr;
      matrixB[1][1] = ystr;
    }
    text(matrixB, dx + 2 * sq, dy  + 2 * sq)
// popMatrix();
   } 

}

int lastX = round(random(sz));
int lastY = round(random(sz));

void mousePressed() {

    setAttractorPull();

    matrixA[0][0] = mouseX - dx;
    matrixA[0][1] = mouseY - dy;
    matrixA[1][0] = lastX - dx;
    matrixA[1][1] = lastY - dy;

    lastX = mouseX;
    lastY = mouseY;

    running = false;
   
}

void mouseReleased() {

   // setAttractorPull();
   running = true;

}

void draw() {

  if (!running) return;

  background(50);
  //line(random(width),random(height),random(width),random(height));

  pushMatrix();
  translate(dx,dy);

  // center quardant box
  stroke(255,156,0);
  strokeWeight(1);
  fill(50,50,50);
  rect(-sq,-sq,2*sq,2*sq);
  rect(-sq/2,-sq/2,sq,sq);
  fill(155,155,155)
  stroke(155,156,0);
  line(-sq, 0, sq, 0);
  line(0, -sq, 0, sq);  
  

  // blue
  stroke(0,156,255);
  strokeWeight(2);

  line(matrixC[0][0],matrixC[0][1],matrixC[1][0],matrixC[1][1]);
  text(matrixA, 0,70); // width/2,height/2);
  multiply(matrixA,matrixB,matrixC); // C = A*B
  //text(matrixA, 0,60); 
  //arrayCopy(matrixC,matrixA); 
  //arrayCopy(matrixC,matrixA); // A = C
  //matrixC = matrixA.reverse().reverse();
  multiply(matrixC,matrixId,matrixA); // A = C*Id = C
  text(matrixA, 0,90); 
  text(matrixB, 30, 0);
  popMatrix();
}


void multiply(matrixA,matrixB,matrixC)
{

  
  for(int i=0; i<2; i++){
           for(int j=0; j<2; j++){
               matrixC[i][j] = 0;
               for(int k=0; k<2; k++){               
               
                 matrixC[i][j]= matrixC[i][j]+ matrixA[i][k] * matrixB[k][j];
              
               }
               matrixC[i][j] = round(matrixC[i][j]*100)/100;
           }
       }
}