HP 41C matrix editor and extend memory

[Ángel Martin]

(08-11-2015 01:12 AM)Les Bell Wrote:  [
The [EMDIR] function just shows the file type as "@" rather than "D" for a data file. It shows the size as being (m x n) as you'd expect, though, i.e. a 4 x 4 matrix is shown as 16 registers.

I presume the unique file type is due to the fact that the ROM often transforms the matrix into an LU (lower-upper) decomposition (e.g. when solving a system of equations or calculating a determinant). The LU decomposition form "is an unrecognizably altered form of a matrix, often containing Alpha data" (p. 52 of the manual). There are lots of dire warnings in that part of the manual.

Yes it is file type "4", and doing a CAT'4 with the OS/X module it displays the "M" character before the size.

The Matrix file header contains richer information than the data or other file types, like the L/U flag as you say - but also the currently selected element.

LU? is a function in the SandMatrix you can use to interrogate whether a matrix has been L/U decomposed or not.

ÁM