Smath does not support reverse cols order in "submatrix".
Alternately, here is the module. Read more in the attached.

Jean



Utilities Matrix Mirror Exercise.sm (19 KiB) downloaded 44 time(s).

I think this is remedied as well with the recent vector indices.
Moreover, I think we can forget about submatrix() function now

http://smath.info/cloud/worksheet/uRMs2euU

Regards,
Radovan

You even don't have to wait for the vector indices, at least for the mirror.

See here



The mirror implementation is straightforward to understand (transpose, reverse, transpose)

The diagonal is a nasty indexing trick, which is that far from paper and pencil notation that it can't be recommended unless you want to obfuscate your algorithm (then best use excel). You just square the row/column index range elements to access the diagonal elements in linear indexing.
This, however, uses the vector index feature.

Wrote

The diagonal is a nasty indexing trick, which is that far from paper and pencil notation that it can't be recommended unless you want to obfuscate your algorithm (then best use excel). You just square the row/column index range elements to access the diagonal elements in linear indexing.
This, however, uses the vector index feature.

diagonal(M):el(M,(range(0,(rows(M)-1)))*(rows(M)+1)+1)