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From |
"Salvati, Jean" <JSalvati@imf.org> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: RE: Re: A Mata question. |

Date |
Mon, 28 Nov 2005 16:02:26 -0500 |

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: owner-statalist@hsphsun2.harvard.edu > > [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of > > adiallo5@worldbank.org > > Sent: Monday, November 28, 2005 7:52 PM > > To: statalist@hsphsun2.harvard.edu > > 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/

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