HP48 Arrays...

[Bill Zimmerly]

Hello!

I'm trying to create an array of simultaneous equations, but the ->ARRY function doesn't seem to be working properly. Can anyone see what I'm doing wrong?

The stack contains:

4: 'X+Y=30'

3: 'Y=Z+2'

2: 'X=14+Z'

1: 3

...and when I issue the ->ARRY function, I get:

->ARRY Error:
Bad Argument Type

I'm totally confused, since the MSLV function REQUIRES an array of the equations!

[Luiz C. Vieira (Brazil)]

Hi.

The ~>ARRY command accepts only numerical entries in the HP48 series. IIRC, the HP49 accepts single variables, but I cannot tell you for sure.

You should try:

[1 1 0]

[0 1 -1]

[1 0 -1]

3

to assemble the coefficient matrix, then

[30]

[2]

[14]

3

to assemble the constants vector. Please, check for possible syntax relevance, I am writing by heart.

One question: the MSLV you mention is the MSOLVR? If so, it demands a list of equations (or expressions, I do not recall correctly) stored in the EQ variable.

Cheers.

Luiz (Brazil)

Edited: 16 Apr 2012, 12:40 p.m.

[Bill Zimmerly]

Thanks Luiz! That does appear to be the problem - that strings can't be arguments for ->ARRY. :(

Also, MSLV is the name of the function I wrote about. If you have the 864 page 48gii user's guide it is described on page 7-4.

[Gilles Carpentier]

Looks correct ... This must works

Can you verify that your equations are TYPE 9. ?

Edit : oups... My reponse is for 49-50 (it works perfectly), I do not know about 48.

Edited: 16 Apr 2012, 12:39 p.m.

[Gerson W. Barbosa]

You might want to try this program. If the stack contains

4: 'X+Y=30'

3: 'Y=Z+2'

2: 'X=14+Z'

1: {X Y Z}

press SYS (F2) to obtain

X (F1)   -->  21.

Y (F2)   -->   9.

Z (F3)   -->   7.

MAT (F4) -->  |1. 1. 0. 30. |

              |0. 1. -1. 2. |

              |1. 0. -1. 14.|

EQS (F5) --> { 'X+Y=30' 'Y=Z+2' 'X=14+Z' } 

[Bill Zimmerly]

Thank you Gerson! :)

[Gilles Carpentier]

With 49/50 you can solve this systems in 2 ways :

1/Use LINSOLVE with vectors

['X+Y=30' 'Y=Z+2' 'X=14+Z']   @ you can use Matrix and equation writer for this

[ 'X' 'Y' 'Z' ]               @ It must be _vectors_ and not matrices ( VEC must be  check in matrix writer : VEC#)              

LINSOLVE                      @ Shift S.SLV  LINSO

->

[ X=21 Y=9 Z=7 ]

This works in symbolic way even with more than 3 unknows for 3 equations

I have forgot that this don't work on 48

                    |x|        |x|    -1

2/ Use matrices : M.|y|=V   => |y| = M  .V

                    |z|        |z|

[[1 1  0]      @  With matrix writer type 

 [0 1 -1]      @ 1 1 0 ENTER RShift <-   v

 [1 0 -1]]     @ 0 1 -1 1 0 -1 ENTER

[[30][2][14]]  @ With matrix writer 30 ENTER 2 14 ENTER

               @ or [] [] 30 -> 2 14 ENTER

SWAP /

->

| 21 |

|  9 |

|  7 |

This works in numeric and symbolic with HP49/50
Only in numeric with my old 48SX (it works here for exemple)

Edited: 16 Apr 2012, 5:12 p.m.

[Gerson W. Barbosa]

You're right! On the HP-49/50g LINSOLVE is a better option, as I've just checked. On the HP-48, AFAIK, there's no built-in command to do it symbolically though.

[Joerg Woerner]

[Allen]

Nice solution!! Curious how you invert that matrix?

[Gilles Carpentier]

You can't because it's not a square matrix :D

Edited: 17 Apr 2012, 7:01 a.m.

[Dave Shaffer (Arizona)]

Quote:

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Curious how you invert that matrix?

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How about this (especially for Joerg!)

[gdeldago]

Quote:

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...

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In fact that is a 4 x 10 matrix ;)

Edited: 16 Apr 2012, 11:40 p.m.

[Reth]

Quote:

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In fact that is a 4 x 10 matrix ;)

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not for the TI fans :)

[Luiz C. Vieira (Brazil)]

This is a unique system: has more solutions in itself than the ones needed to solve it!