Hi,
Warning! I am by no means a mathmatician!
Regarding matrices:
In the alphabet 'x' is before 'y'.
'x' is the horizontal direction and 'y' is the vertical direction of elements of a matrix.
While entering the dimensions of a newly to be created matrix one puts its size in xdirection
into the Xregister and its size in ydirection in the Yregister on the stack.
So far so nice. Logical and understandable. Even for me
And then, entering the matrix editorm, it displays
1:1 <value>
in the first line and pushing > steps to the next element in
xdirection.
But what catch my curiosity: Why are the coordinates in front of the
value of the very element are displayed
y:x <value> ?
x:y <value> would have been seemed more logical to me.
But there must be a reason for it  which?
Same kind of "unlogical setup":
'j' represents the position of an element in xdirection.
'i' represents the position of an element in ydirection.
Why not vice versa ('i'=>x, 'j'=>y), serveing the alphabetical order?
Is there a certain reason for it?
Cheers,
mcc
Questions about handling of matrices by the DM42
Questions about handling of matrices by the DM42
DM 42  SN: 00373, Firmware release v.:3.16. / DMCP 3.20. as compiled by SwissMicros
 PierreMengisen
 Posts: 118
 Joined: Wed Nov 29, 2017 1:38 pm
 Location: Neuchâtel CH
Re: Questions about handling of matrices by the DM42
There is no correspondence between a system of representation in x:y coordinates and the positions in a matrix.
Mathematicians consider a matrix as an arrangement of objects in rows (first) and columns (second).
Indications are always given in this order by the subscripts i and j.
So by moving down in a matrix we increment the index i and by moving to the right we increment index j.
Your confusion comes from your belief in an x and y representation as in the vectorial plane.
greetings
Mathematicians consider a matrix as an arrangement of objects in rows (first) and columns (second).
Indications are always given in this order by the subscripts i and j.
So by moving down in a matrix we increment the index i and by moving to the right we increment index j.
Your confusion comes from your belief in an x and y representation as in the vectorial plane.
greetings
Pierre
[TI59 with PC100C; TI84 Plus CET; HP41CV with HP IL loop & 2*82161A DCD & 82162 TP; HP15C; HP28S; DM41; DM41L; DM42; DM41X]
[TI59 with PC100C; TI84 Plus CET; HP41CV with HP IL loop & 2*82161A DCD & 82162 TP; HP15C; HP28S; DM41; DM41L; DM42; DM41X]

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Re: Questions about handling of matrices by the DM42
The way matrix indices are ordered, with the row index first and the column index second, follows established mathematical convention. For example, see the section "Twodimensional arrays" under "In mathematics" at https://en.wikipedia.org/wiki/Index_notation
Re: Questions about handling of matrices by the DM42
Hi,
thanks for the mathematical infos ...! Now it make more sense to me.
On the other hand: If it is "math speak" to think of a matrix
as an arrangement of "vertical vectors"...why does the matrix
editor fills a matrix "horizontal direction first" then?
Cheers!
mcc
thanks for the mathematical infos ...! Now it make more sense to me.
On the other hand: If it is "math speak" to think of a matrix
as an arrangement of "vertical vectors"...why does the matrix
editor fills a matrix "horizontal direction first" then?
Cheers!
mcc
DM 42  SN: 00373, Firmware release v.:3.16. / DMCP 3.20. as compiled by SwissMicros
Re: Questions about handling of matrices by the DM42
I'd guess because most people read from left to right ...
DM42 SN: 00041 Beta
WP 43S running on this device
HP35, HP45, ..., HP50, WP 34S, WP 31S, DM16L
WP 43S running on this device
HP35, HP45, ..., HP50, WP 34S, WP 31S, DM16L

 Posts: 758
 Joined: Tue May 02, 2017 5:48 pm
 Location: United States
 Contact:
Re: Questions about handling of matrices by the DM42
You can think of a matrix as a collection of vertical vectors or as a collection of horizontal vectors. Both are equally valid. And the HP42S matrix editor is likewise orientationagnostic; if you want to fill a matrix column by column, just press ↓ after each entry instead of → ...
Re: Questions about handling of matrices by the DM42
...I thought at least mathmaticians read from top to bottom...
DM 42  SN: 00373, Firmware release v.:3.16. / DMCP 3.20. as compiled by SwissMicros
 PierreMengisen
 Posts: 118
 Joined: Wed Nov 29, 2017 1:38 pm
 Location: Neuchâtel CH
Re: Questions about handling of matrices by the DM42
No, mathematicians read in n dimensions, where there is neither up nor down, neither here nor there, but all at once. They are poets of the infinite...
Pierre
[TI59 with PC100C; TI84 Plus CET; HP41CV with HP IL loop & 2*82161A DCD & 82162 TP; HP15C; HP28S; DM41; DM41L; DM42; DM41X]
[TI59 with PC100C; TI84 Plus CET; HP41CV with HP IL loop & 2*82161A DCD & 82162 TP; HP15C; HP28S; DM41; DM41L; DM42; DM41X]