Random spot of an array

Lukas

So I have an array and need a random spot of it. The problem is, that I need that spot twice so I can't really use

random(ArrayName);
random(ArrayName);

because I would get two different spots. I also can't do

    var rand = int(random(0, 4));
    arrayName[this.rand];

because the syntax doesn't allow it. I hope you get my point and someone knows an answer. Thanks in advance.

Lukas

PS: I can't mark the code pieces as code for some reason ...

GoToLoop

https://forum.Processing.org/two/discussion/15473/readme-how-to-format-code-and-text

Lukas

Alright I managed to mark the pieces as code :)

GoToLoop

Sorry, but I'm also confused by your question. Need to explain it better. :-\"

Lukas

Ok so I have stored Vectors in that array and I need one of them (a random one) the problem is that I have to call that function twice because I need the x and the y value of that same Vector. That means I cant use

random(ArrayName);
random(ArrayName);

twice because it would get me two different spots. I neither can use

var rand = int(random(0, 4));
arrayName[this.rand];

which would get me the same spot twice (my goal) because the syntax doesn't allow it ... I guess.

Chrisir

Do you have two parallel arrays of type float?

or one array of type PVector?

Your second approach looks good to me:

var rand = int(random(0, 4));
arrayName[this.rand];
point(arrayNameX[this.rand], arrayNameY[this.rand]); 

GoToLoop

Still not getting it... Can't you just store the randomly picked p5.Vector in some temporary variable? :-/

BtW, just made an online example sketch, so you can confirm whether that's what you're looking for. :-\"

Visit here for it: http://CodePen.io/GoSubRoutine/pen/dWeaeg/left?editors=001

/**
 * Vector Array Random Pick (v1.0)
 * GoToLoop (2017-May-13)
 *
 * forum.Processing.org/two/discussion/22573/random-spot-of-an-array#Item_7
 * CodePen.io/GoSubRoutine/pen/dWeaeg/left?editors=001
 */

"use strict";

const VECS = 10, MULT = 10, FRACT = 3,
      SIZE = 48, BOLD = 1.5,
      vecs = Array(VECS);

let bg, cx, cy;

function setup() {
  createCanvas(300, 200).mousePressed(redraw);
  noLoop();

  colorMode(RGB).fill('yellow').stroke('red');
  strokeWeight(BOLD).strokeCap(ROUND);
  textSize(SIZE).textAlign(CENTER, CENTER);

  bg = color('blue');
  cx = width >> 1, cy = height >> 1;

  for (let i = 0; i < VECS; vecs[i++] = p5.Vector.random2D().mult(MULT));
  console.table(vecs);
}

function draw() {
  const {x, y} = random(vecs),
        txt = `x = ${nfs(x, 0, FRACT)}\ny = ${nfs(y, 0, FRACT)}`;

  background(bg).text(txt, cx, cy);
}

Lukas

My complete code is:

var points = [];
var mover;
var ax = 0;
var ay = 0;
var point2;
var bx;
var by;

function setup() {
  createCanvas(1900, 1300);

  this.points.push(createVector(500, 100));
  this.points.push(createVector(1000, 966.026));
  this.points.push(createVector(1500, 100));
  this.mover = createVector(1000, 483);

}

function draw() {
  noStroke();
  fill(51);
  for (var i=0; i<points.length; i++) {
    ellipse(points[i].x, points[i].y, 20, 20);
  }

  noStroke();
  fill(255, 50, 50);
  ellipse(mover.x, mover.y, 5, 5);

  var rand = int(random(0, 4));
  this.ax = (points[this.rand].x + this.mover.x) /2;
  this.ay = (points[this.rand].y + this.mover.y) /2;
  this.mover.x = this.ax;
  this.mover.y = this.ay;
}

I cant use a variable to store the random value, because I can't use that variable to get a spot in the array ....

Lukas

I can even use a variable with a set value like

var var = 1;
ArrayName[this.var].x;
ArrayName[this.var].y;`

But I can't use a variable in which a random value is stored (even if it is an int)

var rand = int(random(0,4));
ArrayName[this.rand].x;
ArrayName[this.rand].y;

Chrisir

why not?

Lukas

It throws an error saying something like "x is undefined". The problem is, that x is not undefined and when I use a variable which is not random it works. I can only get a random spot using:

random(ArrayName);

But then I can't use that same spot twice because the spot is not stored in a variable ...

Lukas

Little Update:

I just fixed the problem with a switch case with a variable of random value. It's a bit complicated but it works... Thank you for you help anyway