Declare new class[].vector3[] length?

I have many arrays of Vector3’s that represent many shapes, each shape is an arrays of dots:

class Dots
    var name : String;
    var dotarray: Vector3[];    
var shape : Dots[];

shape =new Dots[10];//10 shapes

for (var j:int = 0; j < 10; j ++){
	shape[j]=new Vector3[20];//20 dots per shape... this line crashes


BCE0022: Cannot convert ‘UnityEngine.Vector3’ to ‘Dots’.

then i am supposed to access it in this way:

var a_dot = shapej[shapeNumber].dotarray[dotNumber]

Array length = 10, iteration number = 20 : problem.

There are only 10 shapes, so your for loop should be up tp 10, not 20. Also, you want
shape[j].dotarray =new Vector3[20];
You already initialized shape in a previous line, inside the for loop you want to initialize the dotarray of each shape.