What's the Difference Between x_transpose*x and x*x_transpose?

[flufypancakes]

x is a vector - (x1,x2, ..., xn)_transpose (i.e. a column vector). so when we have x_transpose*x we have x1^2+ x2^2+...+xn^2 = norm(x)^2.

right...

now what's x*x_transpose, i.e. column times the row? is it an n-by-n matrix?

actually now that I'm finished typing it I'm pretty sure it is, but i'll still post it to be sure..

 

[Cantab Morgan]

What does your asterisk mean? Sometimes an asterisk means the complex conjugate of a transpose, but I'm not sure that's how you mean it here.

 

[flufypancakes]

* means "times" as in 2*2=4

 

[matt grime]

The definition of matrix multiplication is that when you compose an i by j matrix with a j by k matrix you get an i by k matrix.