koobas.hobune.stream
Find the average of 10 Vectors
I'm trying to find the average of 10 Vector3s, using the following script.
var positions = new Array();
var pos2 = new Array();
var diameter = 3.0;
var numberOfPoints = 10;
var pointObject : Transform;
var n = 0;
var m = Vector3.zero;
var o = Vector3.zero;
var p = new Array ();
private var point : Vector3;
function Start () {
direction();
}
function direction(){
var q = Vector3.zero;
for (i=0; i<numberOfPoints; i++){
positions[i] = m;
positions[i++] = o;
p.Push[m+o];
}
}
Positions is an array which contains the vectors. I get an 'array is out of bounds' error.
Why on earth are you using Array()? All I've ever heard about the Array class is "It's slow, don't use it." List's are usually better, unless you never add or remove anything in which case you use the Vector3[] type of array.
Much of that loop is wrong, I'm afraid. :P
Thor is correct that you're getting the exception because you've incremented i to a number greater than the length of the Array-1, but he's wrong to say that the loop must run while i is less than numberOfPoints-1. Because arrays are zero-indexed, accessing an element at the index i is valid as long as i is less than the length (and greater than or equal to 0), not length-1.
In general, it's bad form to use constant numbers as the limit of array iteration, unless you can be perfectly sure your array's runtime length never deviates from that number. It's always better to use Array.length as the limit in the loop instead of some integer you've set.
In addition to these facts, be mindful of changing your iterator (i) inside the loop: You've got code that says positions[i++] inside the loop body. This can be dangerous business and generally shouldn't be done unless you're absolutely sure about what you're doing. As you know, i++ is short-hand for i = i + 1;, so if you increment i there, then i will get incremented again by the for-loop on the next iteration, causing you to effectively skip an element in the array.
Finally, if the 'average' you want is a single vector that points in the direction you'd be headed if you followed each of the component vectors one by one, the result is just the sum of all the component vectors. Here's a snippet that does that:
Vector3[] vectors = new Vector3[10];
Vector3 average = Vector3.zero;
for (int i = 0; i < vectors.Length; i++)
{
average += vectors[i];
}
Translation to JS is a pretty straight forward. :)
Don't forget to divide the average by the number of Vector3s: average /= vectors.Length;
All previous posts forget to divide through the number of entries.
Try this piece of code:
private Vector3 GetMeanVector(Vector3[] positions)
{
if (positions.Length == 0)
return Vector3.zero;
float x = 0f;
float y = 0f;
float z = 0f;
foreach (Vector3 pos in positions)
{
x += pos.x;
y += pos.y;
z += pos.z;
}
return new Vector3(x / positions.Length, y / positions.Length, z / positions.Length);
}
Another single-line option using LINQ:
List<Vector3> vectors = ...
var averagePosition = vectors.Aggregate(Vector3.zero, (acc, v) => acc + v) / vectors.Count;
As far as I understand, you have to do your loop as long as i is under numberOfPoints - 1 instead of numberofPoints. Otherwise, the line
positions[i++] = o;
while raise a "Out of bounds" exception.
But this works only when your "Position" array is initialized with "numberOfPoints" position...
Hope it's helped !
Cheers, Thor
