Divide skalar/locals and input result into matrix

[Any Mary]

Dear all,
I need to devide one scalar/local through another and input the result into a matrix.
In the following, you find a simplified version of the syntax, which i use:

mata: st_numscalar("sum", z)
count
local a = r(N)
scalar define b = `sum'/`a' // (1) here scalar/local one ist divided through another
matrix define B = (.,.\.,.)
matrix B[1,1] = `b' // (2) here the result is entered into a matrix

Unfortuantely, neither step (1) nor (2) works. Can somebody help me to definie a version of the syntax, which works?

[Nick Cox]

A numeric scalar is not a local macro. With that fixed and some other simplifications try

mata: st_numscalar("sum", z)
count
scalar b = sum/r(N)
matrix B = (.,.\.,.)
matrix B[1,1] = b

or even

mata: st_numscalar("sum", z)
matrix B = (.,.\.,.)
matrix B[1,1] = sum/_N

or even

mata: st_numscalar("sum", z)
matrix B = (sum/_N, . \ . , .)

I quite often see programming practice of the following form:

I have a pen. I put it in a box. I want to use my pen. I take it out of the box.

With nothing else said, the box part can be omitted.

In this case, you defined a scalar b. That is the boxing. No harm in that, but nevertheless did you really need the scalar? If you are going to use it later, and especially more than once, that is a good idea, but not otherwise.

[Any Mary]

Dear Nick,
thanks for your quick help, your general advice and special advice to further simplify my syntax!
The problem is solved in a very elegant way now.
Best