HP 41C matrix editor and extend memory

[mbrethen]

The matrix editors on the hp41 advantage module can store matrices directly to extended memory. Does anyone know what file type is created? Secondly, is it possible to plot the data? For example, if I have stored two column matrices in extended memory is it possible to plot one against the other (similar to a residual versus predicted plot in regression analysis) using prplot or the plot programs on the ppc module?

[Les Bell]

(08-11-2015 12:03 AM)mbrethen Wrote:  Does anyone know what file type is created?

According to p. 33 of the manual, "A matrix in extended memory has a file length of m x n (2m x 2n for a complex matrix). Its file type is unique to matrices. Do not use the function [CLFL] with a matrix in extended memory: this destroys part of the file's header information. Instead, use [PURFL] to purge the entire matrix".

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.

[Ángel Martin]

(08-11-2015 12:03 AM)mbrethen Wrote:  The matrix editors on the hp41 advantage module can store matrices directly to extended memory. Does anyone know what file type is created? Secondly, is it possible to plot the data? For example, if I have stored two column matrices in extended memory is it possible to plot one against the other (similar to a residual versus predicted plot in regression analysis) using prplot or the plot programs on the ppc module?

The SandMatrix Module manual has some additional information on the matrix file structure. It includes all the matrix functions from the Advantage plus many more on that subject. It also includes a "quick entry" mode using complete rows as inputs, as opposed to by single elements.

Look for "Sandmatrix" at TOS to download your copy.

I have a program to print matrices on the Thinkjet or 82905B - I can share it if anyone cares.

Cheers,
ÁM

[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