Functions with Variable Numbers of Arguments: Outer Vector Product

Question

I am trying to write a function that takes a column vector of variable dimension as an input and returns the outer product matrix as an output.

What I have tried:

OuterVectorProduct[x__] := MatrixForm[Outer[Times, x, x]]

However, this obviously returns wrong results.

Thanks!

Answer 1

Here is a simple example that will get you started,

x = {x1, x2, x3};
y = {y1, y2};

(xy = KroneckerProduct[x, y]) // MatrixForm

(* get 3x2 matrix output *) 

(yx = KroneckerProduct[y, x]) // MatrixForm 

(* get 2x3 matrix output *) 

The parentheses are important --- compare the FullForm of the resulting "matrix" if you leave them out.

Edit:

In answer to your specific Qn,

OuterVectorProduct[x_] := KroneckerProduct[x, x]

which will work for a vector x for any value of Dimensions[x].