Benn Jann wrote:
> Matrix subscripts are typed in brackets.
I think what Amadou wants is an array or "collection" of matrices. And
Amadou is confused because macro substitution doesn't work.
I have very little experience with MATA, but it seems to me that the
desired result can be achieved using pointers and arrays of pointers.
Here is an example. For i=1 to i=10, the following program creates and
displays a 2x2 matrix filled with i:
mata
// declare an array of NULL pointers
P = J(10,1,NULL)
for (i=1;i<10;i++) {
// create a matrix and assign its address to P[i]
P[i] = &(J(2,2,i))
// just make sure that all the elements of P don't point
to the same matrix
}
for (i=1;i<10;i++) {
i
// dereference the i-th element of P to get the i-th
matrix in the "collection"
*(P[i])
}
end
The alternative is to create a single big matrix and extract rows from
that matrix as needed.
Jean Salvati
> > -----Original Message-----
> > From: [email protected]
> > [mailto:[email protected]] On Behalf Of
> > [email protected]
> > Sent: Monday, November 28, 2005 7:52 PM
> > To: [email protected]
> > Subject: st: Re: A Mata question.
> >
> >
> > Thanks Nick for the answer.
> > My other question is how to create
> > new matrix within loops?
> > I am puzzled by the fact that there is no `i'
> > in mata's loops as in normal stata.
> > Best regards.
> > Amadou.
> >
> > mata:
> > A1 = (1,2,3\4,5,6)
> > A1
> > A2 = (1,2,3\4,5,6)
> > A2
> > B1=A1
> > B1
> > B2=A2
> > B2
> > for (i=1;i<=2;i++) {
> > i // just to display the increment
> > C(i) = A(i) // ??? I tried Ci = Ai and C`i' = A`i' plus various
> > variants (==, (), etc...) with no success
> > C(i) // display
> > }
> > end:
> >
> >
> > *
> > * 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/
> >
>
> *
> * 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/
>
*
* 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/
