Using -syntax- to get Mata matrix definitions and evaluating these in Mata

[Niels Henrik Bruun]

Hi
I would like to build a Stata command retrieving a string definition of a Mata matrix, evaluate it and send the matrix into some mata code.
So I started with numbers and all went well:

. clear
. mata mata clear
. local 0 , code(1, 2 \ 3, 4)     // Setting up input to test syntax
. syntax, code(string)
. capture mata M = `code'         // Evaluating mata matrix
. if _rc mata M = J(0,0,.)        // Default value if error evaluating
. mata M
       1   2
    +---------+
  1 |  1   2  |
  2 |  3   4  |
    +---------+

Nice!! An easy way to pass matrices from Stata to Mata.

Now I need to do this for both real and string matrices, so I went on:

. clear
. mata mata clear
. local 0 , code("l", "r" \ "c", "r")     // Setting up input to test syntax
. syntax, code(string asis)
. capture noisily mata M = `code'         // Evaluating mata matrix
. if _rc mata M = J(0,0,"")               // Default value if error evaluating
. mata M
       1   2
    +---------+
  1 |  l   r  |
  2 |  c   r  |
    +---------+

The key point is to use asis defining string input in the -syntax- command when evaluating string matrices.
Using asis when evaluating real matrices doesn't change a thing, so one could choose to use asis always in cases like this.


Similar things has been discussed previously in http://www.stata.com/statalist/archi.../msg00775.html and in http://www.stata.com/statalist/archi.../msg00925.html


Hopefully someone finds this usefull