hi.
if P were:
(1 2 3)
(4 5 6)
(7 8 9)
vec(P) would be vec(P) = (1 4 7 2 5 8 3 6 9)^t.
M is a matrix with the elements of vec(X) on its diagonal and 0 everywhere else. In notations, M = Diag(vec(X)). For simplicity, we can assume that M is binary.
I think we were having trouble...
hi.
I think I already defined Y to be n^2 by n^2 (read my first post). i am sorry if you got the impression that Y is of size 1 by 1. By P', I wanted to say transpose(P). Matlab does it this way. You can construct p from P by considering rows/columns appended one after the other. If P is a n...
hi.
What I meant by equivalence is that
vec(P*X*P')==transpose(M)*Y
I want to know if this statement is true or not. As before P is a n by n perm matrix, X is a n by n matrix. Y=vec(P)*vec(P)' which is n^2 by n^2 and M=vec(X) which is n^2 by 1. If this does not hold, can we do the same using...
hi all
I have a simple question relating to permutation matrices.
We have an a matrix, X. We have a permutation matrix, P. We can get the permuted version of X by doing
permutedX = P*X*P'.
Now, I want to represent the matrices in vector form. The way the books mention it as follows.
They...
thanks all for your replies. yeah, it does make sense if i think of it as hallsofivy pointed out : the set of all vectors whose dot product with e[sub]k[sub] is 0.
this is how the author gets to the part in the paper
Z is a n-by-n projection matrix satisfying Z^2 = Z. e is the same as i...
Hi:
was wondering if somebody can help me with this I came across in a paper.
$e_k$ is a vector of $k$ $1's. M is a matrix of size n \times k. The author talks about projecting $M$ onto the null space of $e_k$. This is what confuses me. Which $x$ apart from the 0-vector solves e_kx=0...
hi:
I am faced with an integration problem and can't seem to get even Maple/Mathematica to solve it. Would really appreciate if somebody can help me here. An approximate solution will also help.
\int_{-R}^{R}{cos(2\pi\nu x}) e^{-2\mu{\sqrt{R^2 - x^2}}}dx
thanks a lot for your time.