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st: Re-access a matrix in mata through a mata function


From   Ly Tran <lyhuyen@brandeis.edu>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re-access a matrix in mata through a mata function
Date   Wed, 30 Jan 2013 11:30:04 -0500

So I have this large matrix (appx. 5000x5000) in Mata (the Stata
version that I have does not allow a matrix of that size in Stata).

To fill up this matrix, I have to run 5000 repetitions, each time
adding the calculated values into one column of the matrix. This part
is in an ado file that I wrote, so in order to update the matrix, I
had to do this:
forval i = 1/5000 {
      .... // calculating the new values, save it in variable X
     mata: R[i,.] = X'  // this is just a gist of it, my actual code
is a couple of lines longer
}

I would like to put those couple of lines "mata: R[i,.] = X'" into a
mata function. But when I right a function,
mata
     void updateR(real scalar i) {
           R[i,.] = X'
     }
end,
the matrix R does not exist within the function, so the error is
always "Subscript invalid". Again, let's assume that in my actual
program, I take care of the validity of i and X.

I just wonder if there is anyway to solve this problem, i.e. accessing
R through a mata function. The next part requires a lot of work with
R, so I would really like to write a function/program for it, instead
of doing "mata:" for the next hundred lines.

Is there a way for me to stick with Stata instead of using Matlab to
write this program?

Thank you.


But the next part is to

--
Ly Tran
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