Re: Algorithm for Vector Cross Product of N Dimensions

From:
 hobbes <sardonicStuffedTiger@gmail.com>
Newsgroups:
comp.lang.java.programmer,sci.math
Date:
Wed, 22 Aug 2007 19:15:34 -0000
Message-ID:
<1187810134.882507.96060@q4g2000prc.googlegroups.com>
so just to clarify what i am doing, for reasons unknown i am making a
vector class in java and i want the vector object to be able to
perform all the operations that can be performed on a vector. the way
i am doing it now it could be possible to do this:

Vector v2d = new Vector(1, 2);
Vector v3d = new Vector(3, 4, 5);
Vector vx = v2d.cross(v3d);

i guess it should throw an exception here? i was looking for some
algorithm that could compute the cross product of vectors of arbitrary
length but it doesn't sound like i should be doing that in the first
place?

i also stumpled upon the java3d library and i think they are already
doing something like this but so far i dont like/understand the api
and it's kind of fun to do this anyway. but i notice their vector
classes inherit from tuple. is a vector a form of tuple and is the
cartesian product of a tuple the same as the cross product of a
vector? if so, can someone recommend an algorithm laid out somewhere i
can reference?

Patricia Shanahan wrote:

What exactly do you mean by "mathematically correct", and what is the data=

 type of the >input? The formula would be easiest to apply, in Java, in dou=
ble, but that would involve >rounding error. If you choose one of the repre=
sentations that only involves addition, >subtraction, and multiplication yo=
u could do it exactly in BigDecimal.

so the vector coordinates could be read as int, float, or double for
what i am doing and actually the coordinates are stored as an array of
Point2D objects so that I can store the initial and terminal points in
pairs, which on second thought should be tuples which contain pairs of
"Number" instead of primitives?

public Vector(double... c) {
    this.coordinates = new Point2D[c.length];
    for (int i = 0; i < c.length; i++)
        this.coordinates[i] = new Point2D.Double(0, c[i]);
    //overloaded constructors create Point for int, Point2D.Float for
float
}//constructor

the operations from there on out are basically manipulating the values
in the array.

Patricia Shanahan wrote:

Is it possible that you meant "outer" rather than "cross"?


i did mean cross product. i dont think i ever learned outter product
but it sounds like something i should implement at some point. 

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