constructor(x,y){

    this.x=x

    this.y=y

  }

  tegn(){

    strokeWeight(5)

    point(xCoord(this.x),yCoord(this.y))

    strokeWeight(1)

  }

}

class funktion{

  constructor(a,b){

    this.a=a

    this.b=b

  }

  værdi(x){

    if(e==0){

      return this.a*x+this.b

    } else if(e==1){

      return this.b*pow(this.a,x)

    }

  }    

  graf(){

    if(e==0){

      line(0,yCoord(this.værdi(-O[0]/xZoom)),w,yCoord(this.værdi((w-O[0])/xZoom)))

    } else if(e==1){

      let j=0

      while(yCoord(this.værdi((j+1-O[0])/xZoom))>0){

        line(j,yCoord(this.værdi((j-O[0])/xZoom)),j+1,yCoord(this.værdi((j+1-O[0])/xZoom)))

        j++

      }

    }

  }

  regina(a) {

    if (a.length > 1) {

      let sX = 0;

      let sY = 0;

      let sXY = 0;

      let sXX = 0;

      for (let i = 0; i < a.length; i++) {

        sX += a[i].x;

        sY += a[i].y;

        sXY += a[i].x * a[i].y;

        sXX += sq(a[i].x);

      }

      this.a = (a.length * sXY - sX * sY) / (a.length * sXX - sq(sX));

      this.b = (sXX * sY - sX * sXY) / (a.length * sXX - sq(sX));

      if(e==1){

        this.a=exp(this.a)

        this.b=exp(this.b)

      }

    }

  }

  res(a) {

    let b = [];

    for (let i = 0; i < a.length; i++) {

      b.push(a[i].y - this.værdi(a[i].x));

    }

    return b;

  }

  rSq(a) {

    let Sr = 0;

    let Sy = 0;

    let My = 0;

    for (let i = 0; i < a.length; i++) {

      Sy += a[i].y;

    }

    My = Sy / a.length;

    Sy = 0;

    for (let i = 0; i < a.length; i++) {

      Sr += sq(this.res(a)[i]);

      Sy += sq(a[i].y - My);

    }

    return 1 - Sr / Sy;

  }

}

let xIn;

let yIn;

let uXin;

let uYin;

let sXm = 0;

let sYm = 0;

let e = 0;

let p = 0;

let nE = 0;

let nP = 0;

let tX = 40;

let tY = 0;

let t1w = 50;

let t2w = 40;

let m = 20;

let PmiX;

let PmaX;

let rP=200

let w=900

let h=550

let P=[[],[]]

let eP=[]

let xZoom=20

let yZoom=20

let O=[w/2,h/2]

let f=new funktion(4,9)

function setup() {

  createCanvas(w, h+rP);

  xIn = createInput("");

  xIn.position(tX, tY + 2 * m);

  xIn.size(t1w);

  yIn = createInput("");

  yIn.position(tX, tY + 20 + 2 * m);

  yIn.size(t1w);

  uXin = createInput("");

  uXin.position(tX + t1w, tY + 2 * m);

  uXin.size(t2w);

  uYin = createInput("");

  uYin.position(tX + t1w, tY + 20 + 2 * m);

  uYin.size(t2w);

}

function draw() {

  background(220);

  textSize(20);

  text("Funktionsforskfriften er", tX + t1w + t2w + 10, tY + 20 + 2 * m);

  //if(keyIsDown(69)){e=1}

  if(keyIsDown(76)){e=0}

  if(keyIsDown(69)){e=1}

  if (keyIsDown(13) && xIn.value() != "" && yIn.value() != "") {

    P[0].push(new punkt(float(xIn.value()), float(yIn.value())));

    P[1].push(new punkt(float(xIn.value()), float(log(yIn.value()))));

    PmiX = min(PmiX, float(xIn.value()));

    PmaX = max(PmaX, float(xIn.value()));

    xIn.value("");

    yIn.value("");

  }

  f.regina(P[e])

  if (keyIsDown(RIGHT_ARROW)) {

    if (keyIsDown(16)) {

      xZoom = xZoom * 1.01;

      O[0]=-w/2*0.01+O[0]*1.01

    } else {

      O[0] += 1;

    }

  }

  if (keyIsDown(LEFT_ARROW)) {

    if (keyIsDown(16)) {

      xZoom = xZoom / 1.01;

      O[0]=w/2*0.01/1.01+O[0]/1.01

    } else {

      O[0] -= 1;

    }

  }

  if (keyIsDown(UP_ARROW)) {

    if (keyIsDown(16)) {

      yZoom = yZoom * 1.01;

      O[1]=-h/2*0.01+O[1]*1.01

    } else {

      O[1] -= 1;

    }

  }

  if (keyIsDown(DOWN_ARROW)) {

    if (keyIsDown(16)) {

      yZoom = yZoom *0.99;

      O[1]=h/2*0.01/1.01+O[1]/1.01//(O[1]-C)*0.99+C

    } else {

      O[1] += 1;

    }

  }

  for(let i=0;i<P[e].length;i++){

    P[0][i].tegn()

    text("(" + P[e][i].x + "," + P[e][i].y + ")", 2 * m, 2 * m + 20 * (i + 3));

      strokeWeight(5);

      point(

        m + ((w - 2 * m) / (PmaX - PmiX)) * (P[e][i].x - PmiX),

        h +

          rP / 2 -

          (((rP - m) / max(max(f.res(P[0])), -min(f.res(P[0])))) * f.res(P[0])[i]) / 2

      );

      strokeWeight(1);

  }

  if(e==0){

    text(

      "f(x)=" + round(f.a, 2) + "x+" + round(f.b, 2),

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

  } else {

    text(

      "f(x)=" + round(f.b, 2) + "*" + round(f.a, 2)+"^x",

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

  }

    text("r^2=" + f.rSq(P[0]), tX + t1w + t2w + 10, tY + 60 + 2 * m);

    line(0, h + rP / 2, w, h + rP / 2);

  strokeWeight(1);

  text(

    "(" +

      round((m - O[0]) / xZoom, 1) +

      "," +

      round((O[1] - h + 20) / yZoom, 1) +

      ")",

    30,

    h - 30

  );

  f.graf()

  if (O[0] < m) {

    line(m, 0, m, h);

    stroke(0);

    text(uYin.value(), m + 10, m + 5);

  } else if (O[0] > w - m) {

    line(w - m, 0, w - m, h);

    stroke(0);

    textAlign(RIGHT);

    text(uYin.value(), w - 3 * m, m + 5);

    textAlign(LEFT);

  } else {

    stroke(0);

    line(O[0], 0, O[0], h);

    text(uYin.value(), O[0] + 5, m + 5);

  }

  stroke(150);

  if (O[1] > h - m) {

    line(0, h - m, w, h - m);

    stroke(0);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, h - 3 * m);

    textAlign(LEFT);

  } else if (O[1] < m) {

    line(0, m, w, m);

    stroke(0);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, 2 * m + 10);

    textAlign(LEFT);

  } else {

    stroke(0);

    line(0, O[1], w, O[1]);

    textAlign(RIGHT);

    text(uXin.value(), w - m + 5, O[1] - m * 0.5);

    textAlign(LEFT);

  }

  stroke(150);

  line(m, 0, m, h);

  line(w - m, 0, w - m, h);

  line(0, m, w, m);

  line(0, h - m, w, h - m);

  stroke(0);

}

function mousePressed() {

  mX = mouseX;

  mY = mouseY;

}

function mouseReleased() {

  dX = mouseX - mX;

  dY = mY - mouseY;

  if (keyIsDown(16)) {

    xZoom = xZoom * pow(1.01, dX);

    O[0] = (w / 2) * (1 - pow(1.01, dX)) + O[0] * pow(1.01, dX);

    yZoom = yZoom * pow(1.01, dY);

    O[1] = (h / 2) * (1 - pow(1.01, dY)) + O[1] * pow(1.01, dY);

  } else {

    O[0] += mouseX - mX;

    O[1] += mouseY - mY;

  }

}

function xCoord(x){

  return x*xZoom+O[0]

}

function yCoord(y){

  return O[1]-y*yZoom

}