let S = 100; 

let Z = 0;

let P = 0;

let R = 0;

let I = 0; 

​

let t = 0;

​

//birth 

let Pi = 10;

​

//removed death

let delta = 0.01;

​

//potential death

let gamma = 0.04;

​

//resuraction rate

let zeta = 0.02;

​

//stun rate

let alph = 0.04;

​

//kill rate 

let nu = 0.03; 

​

//infection rate 

let beta = 0.01; 

​

//move on 

let p = 0.5;

​

function nonZero(a,b){

  if(a + b >= 0){

    return a

  }else{

    return -b;

  }

}

​

function zombies(){

  t ++;

  console.log("--------------"+t+"--------------");

  //der

  let S_ = 0;

  let P_ = 0;

  let R_ = 0;

  let Z_ = 0;

  let I_ = 0;

  //calc der

  S_ = Pi - delta*S - gamma*S;

  P_ = gamma*S - zeta*P + alph*S*Z;

  R_ = delta*S + nu*S*Z;

  Z_ = zeta*P - alph*S*Z - nu*S*Z + p*I;

  I_ = beta*S*Z - p*I - delta*I; 

  //add der

  let roundedS_ = floor(S_);

  let roundedP_ = floor(P_);

  let roundedR_ = floor(R_);

  let roundedZ_ = floor(Z_);

  let roundedI_ = floor(I_)

  let nonZeroS_ = nonZero(roundedS_,S);

  let nonZeroP_ = nonZero(roundedP_,P);

  let nonZeroR_ = nonZero(roundedR_,R);

  let nonZeroZ_ = nonZero(roundedZ_,Z);

  let nonZeroI_ = nonZero(roundedI_,I);

  //display rate of change

  console.log("dS: ",nonZeroS_," dP: ",nonZeroP_," dR: ",nonZeroR_," dZ: ",nonZeroZ_, " dI: ",nonZeroI_);

  S += nonZeroS_;

  P += nonZeroP_;

  R += nonZeroR_;

  Z += nonZeroZ_;

  I += nonZeroI_;

  //dislay change

  console.log("S: ",S," P: ",P," R: ",R," Z: ",Z," I: ", I);

}

​

function setup() {

  createCanvas(400, 400);

}

​

function draw() {

  background(220);

}

​

function mouseClicked(){

  zombies();

}