HP-50g Algebraic matrix expressions

[Sleazey]

I usually do all my HP50 programming in RPL. And it has been a few years since I needed to do anything non-trivial.

But I have a need to use algebraic syntax for some complex expressions involving matrices, since the algebraic form is easier to verify visually for correctness.

How do I refer to a single element of a matrix variable with an algebraic expression?

"matrix1", "r", and "c" are all local variables in the current program fragment. I want to refer to the element in matrix1 at row r, column c.

The obvious approach generates an error when I try to save from the command line:
'matrix1[r,c]'.

This does not work.

I have tried several obvious variations, but none of them work:
'matrix1[[r,c]]'
'matrix1[r c]'
'matrix1[[r c]]'

Is what I am asking even possible with algebraic expressions?

If so, what is the correct syntax? I have been unable to find any examples online of using subscripts for a matrix in an algebraic expression. Any pointers to such would be welcome!

Thanks everyone!