constructor(x,y){

    this.x=x

    this.y=y

  }

  place(){

    strokeWeight(5)

    point(O[0]+skalX*this.x,O[1]-skalY*this.y)

  }

}

class lin{

  constructor(a,b){

    this.a=a

    this.b=b

  }

  værdi(x){

    return this.a*x+this.b

  }

  graf(){

    strokeWeight(1)

    line(0,O[1]-this.værdi(-O[0]/skalX)*skalY,w,O[1]-this.værdi((w-O[0])/skalX)*skalY)

  }

  reg(p){

    let sXY=0

    let sX=0

    let sY=0

    let sXX=0

    for(let i=0;i<p.length;i++){

      sXY+=p[i].x*p[i].y

      sX+=p[i].x

      sY+=p[i].y

      sXX+=sq(p[i].x)

    }

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

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

  }

  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 f = new lin(2, 4);

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 rP=200

let PmiX

let PmaX

let P=[]

let skalX=50

let skalY=50

let w=900

let h=550

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

​

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

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

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

    f.reg(P)

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

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

    xIn.value("");

    yIn.value("");

  }

  if (keyIsDown(RIGHT_ARROW)) {

    if (keyIsDown(16)) {

      sX = sX * 1.01;

      O[0]=-w/2*0.01+O[0]*1.01

    } else {

      O[0] += 1;

    }

  }

  if (keyIsDown(LEFT_ARROW)) {

    if (keyIsDown(16)) {

      sX = sX / 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)) {

      sY = sY * 1.01;

      O[1]=-h/2*0.01+O[1]*1.01

    } else {

      O[1] -= 1;

    }

  }

  if (keyIsDown(DOWN_ARROW)) {

    if (keyIsDown(16)) {

      sY = sY *0.99;

      O[1]=h/2*0.01/1.01+O[1]/1.01

    } else {

      O[1] += 1;

    }

  }

  for(let i=0;i<P.length;i++){

    P[i].place()

    strokeWeight(1)

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

    strokeWeight(5);

      point(

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

        h +

          rP / 2 -

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

      );

      strokeWeight(1);

  }

  text(

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

      tX + t1w + t2w + 10,

      tY + 40 + 2 * m

    );

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

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

    text(

    "(" +

      round((m - O[0]) / skalX, 1) +

      "," +

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

      ")",

    30,

    h - m - 10

  );

  textAlign(RIGHT);

  text(

    "(" + round((w - m - O[0]) / skalX, 1) + "," + round((O[1] - m) / skalY, 1) + ")",

    w - m - 10,

    m + 20

  );

  f.graf()

  strokeWeight(1);

  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)) {

    skalX = skalX * pow(1.01, dX);

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

    skalY = skalY * 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;

  }

}