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st: Function el() fails

From   "Sergiy Radyakin" <[email protected]>
To   "[email protected]" <[email protected]>
Subject   st: Function el() fails
Date   Fri, 15 Aug 2008 17:54:44 -0400

Dear All,

after investigating why my program sometimes breaks, I have found a
problem (observed in Stata 9 and Stata 10 for Windows) with the
function el(matrixname, row, col ), which could be reproduces with the
following sequence of commands:

// ----- BEGIN -------
   sysuse auto

   matrix p=1
   matrix a=p

   matrix dir

   matrix list a
   di a[1,1]
   di el(a,1,1)

   matrix list p
   di p[1,1]
   di el(p,1,1)
// ----- END -------

According to the help file for Stata 9:

 el(A,i,j)       the i,j element of A (same as A[i,j])

Note that the program above works for matrix name "a" and not "p".
This made it difficult to identify the problem. Because the problem is
observed for some datasets and not for others.

It seems that the namespace of variables and matrix names in Stata is
I've met the messages earlier regarding what namespaces are shared,
but I can't find them at the moment. The manual explicitly defines the
term "namespace" in the [P] matrix, (page 235 in 10th edition). It
also mentions that there is a single namespace for scalars and
matrices, however it does mention variables in a rather confusing

"Scalars and matrices share the same namespace; i.e., scalars and
matrices may have the same names as variables in the dataset, etc.,
but they cannot have the same names as each other."

Confusion here is that indeed Stata allows me to have a matrix with
the same name as a variable, but I'd really like the built-in commands
and functions to be able to WORK with that matrix. (Function el() as
all functions in Stata is built-in).

I wonder if anyone could elaborate on which namespaces are shared in
Stata, in particular:

all sort of mata objects
all sort of graphics related styles, patterns, etc
[not sure how long the list is, but the above list is definitely not complete]

I am not sure that the problem above is an intended behavior. In any
case it makes the case that el(a,1,1) is NOT equivalent to A[1,1]
against what the help file says.
If this is not an intended behaviour, can this be fixed?

Thank you,
Sergiy Radyakin

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