How to rotate a array with x, y values?

Question

So i have array that can look like this (javascript for the matter):

array = [{x: 0, y: 0}, {x: 1, y: 1}, {x: -4, y: 3}]

Each of the entrys has a x and y position. What i want to do is essentialy rotate those entrys 90 degrees in one direction.

Whats the simplest way to do this?

The center of the rotation is $(0,0)$? Counter-clockwise? – Frostic Apr 23 '18 at 17:55 — Frostic, Apr 23 '18 at 17:55

Frostic · Accepted Answer · 2018-04-25T15:03:54.873

1

Basically you could something like this to perform a counter clockwise $90$ degrees rotation of center $(0,0)$. The point $(x,y)$ is transformed in $(-y,x)$.

c=x
x=-y
y=c

One liner javascript code:

[x, y] = [-y, x];

Drawing it should convince you. You could look at rotation matrices for solutions of broader problems with a different angle for example.

edited Apr 25 '18 at 15:03

answered Apr 23 '18 at 18:02

Frostic

1,262

This rotates 180 – Vajura Apr 24 '18 at 08:46
Oops yes I corrected it – Frostic Apr 24 '18 at 14:34

score 1 · Answer 2 · answered Apr 23 '18 at 18:06

1

What about iterating over the array, converting each pair $(x, y)$ to a complex number, using for instance Complex.js, and multiplying by the imaginary unit $i$, which corresponds to a rotation of 90 degrees counterclockwise.

answered Apr 23 '18 at 18:06

Ivar Stangeby

321

How to rotate a array with x, y values?

2 Answers2