Kit Baum wrote > I've never heard of a 'horizontal direct product' but in a 2x2
> example it seems to be the first and last rows of a conventional
> Kronecker product...
the term "horizontal direct product" is used in Gauss manual ( and R i
think) and denoted by the operator
" *~ " and is different from the kronecker product in Gauss denoted by " .*. "
You are right when tou say that "it appears that whatever this
construction might be it
> could be generated from a Kronecker" but the question is how to automate such task in Mata. You know that with matrix A(k,l), B(m,n) ; A#B =C(k*m,l*n) but here we want a new matrix C(k,l*n) asumming that k=m. Hence my motivation to write my hdp() function
AbdelRahmen
2007/10/19, Kit Baum <[email protected]>:
> Abdel wrote
>
> I've written this mata function as a solution to my own question
> yesterday.
> horizontal direct product (hdp).
> --------begin code------------
> version 9.2
> local mydir "."
> mata:
> mata clear
> real matrix hdp(real matrix A, real matrix B)
> {
> assert(rows(A)==rows(B))
> real scalar n
> real matrix C
> n=rows(A)
> C=J(n,1,.)
> for (i=1; i<=cols(A); i++) {
> C=C,(A[.,i]:*B)
> }
> C=C[.,2..cols(C)]
> return(C)
> }
>
>
> I've never heard of a 'horizontal direct product' but in a 2x2
> example it seems to be the first and last rows of a conventional
> Kronecker product:
>
> : a
> 1 2
> +---------+
> 1 | 1 2 |
> 2 | 3 4 |
> +---------+
>
> : b
> 1 2
> +---------+
> 1 | 5 6 |
> 2 | 0 1 |
> +---------+
>
> : c
> 1 2 3 4
> +---------------------+
> 1 | 5 6 10 12 |
> 2 | 0 3 0 4 |
> +---------------------+
>
> : a#b
> 1 2 3 4
> +---------------------+
> 1 | 5 6 10 12 |
> 2 | 0 1 0 2 |
> 3 | 15 18 20 24 |
> 4 | 0 3 0 4 |
> +---------------------+
>
>
> For a 3x3 example, it is the 1st, 5th and 9th rows of the Kronecker
> product. Thus it appears that whatever this construction might be it
> could be generated from a Kronecker.
>
>
>
>
> Kit Baum, Boston College Economics and DIW Berlin
> http://ideas.repec.org/e/pba1.html
> An Introduction to Modern Econometrics Using Stata:
> http://www.stata-press.com/books/imeus.html
>
>
> *
> * For searches and help try:
> * http://www.stata.com/support/faqs/res/findit.html
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
--
AbdelRahmen El Lahga
*
* For searches and help try:
* http://www.stata.com/support/faqs/res/findit.html
* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
