Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Old July 4th 04, 03:48 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2004
Posts: 1
Default solving a matrix in Excel

Hi,

I am wondering how to solve an 8x8 matrix using Excel equations.

Supposing the situation is

column
A B C D E F G H I
1 7 4 2 9 .... 2| 5
2 10 3 6 ... | 1
r 3 2 ... |
o 4 .
w 5 . data
6
7
8

In other words, it is solving the system

A1*x[1]+B1*x[2]+C1*x[3]+D1*x[4]+E1*x[5]+F1*x[6]+G1*x[7]+H1*x[8]=I1
A2*x[1]+B2*x[2]+C2*x[3]+D2*x[4]+E2*x[5]+F2*x[6]+G2*x[7]+H2*x[8]=I2
A3*x[1]+B3*x[2]+C3*x[3]+D3*x[4]+E3*x[5]+F3*x[6]+G3*x[7]+H3*x[8]=I3
..
..
A8*x[1]+B8*x[2]+C8*x[3]+D8*x[4]+E8*x[5]+F8*x[6]+G8*x[7]+H8*x[8]=I8

I have already done this but my answers are wrong. It took several
manipulations and created about 16 blocks on the spreadsheet in 230
rows. In its final form the solution should have a diagonal of all 1's
between A1 and H8 and the rest zeros, except column I should be the
solutions to each x[1],x[2],..,x[8].

Does anyone know what I'm talking about? Any help would be appreciated.
Is there a formula that will compute the matrix all in one formula?

Jon


  #2   Report Post  
Old July 4th 04, 04:34 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2006
Posts: 2,253
Default solving a matrix in Excel

Jon,

as you supposed.. excel DOES have a function for it:
see help for MDETERM().. and related MMULT() and MINVERSE()

keepITcool

< email : keepitcool chello nl (with @ and .)
< homepage: http://members.chello.nl/keepitcool


Jon wrote:

Hi,

I am wondering how to solve an 8x8 matrix using Excel equations.


Does anyone know what I'm talking about? Any help would be appreciated.
Is there a formula that will compute the matrix all in one formula?

Jon



  #3   Report Post  
Old July 4th 04, 07:05 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2006
Posts: 733
Default solving a matrix in Excel

"Jon" wrote...
I am wondering how to solve an 8x8 matrix using Excel equations.

....
A1*x[1]+B1*x[2]+C1*x[3]+D1*x[4]+E1*x[5]+F1*x[6]+G1*x[7]+H1*x[8]=I1

....
A8*x[1]+B8*x[2]+C8*x[3]+D8*x[4]+E8*x[5]+F8*x[6]+G8*x[7]+H8*x[8]=I8

....

So y = A x. *Left* multiply both sides of the equation by the inverse of A
and what do you get? See MMULT and MINVERSE in online help.


  #4   Report Post  
Old July 6th 04, 03:10 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2004
Posts: 1
Default solving a matrix in Excel

Hi,

I solved the matrix using standard row operations. Then I used x=A^-1
*b in Excel and all I got was garbage. My first results showed
virtually no error. The commands I used in Excel were,

=MINVERSE(AA1:AH8) (Saved in AA11:AH18)
=MMULT(AA11:AH18,AI1:AI8) (Saved in AI21:AI28)

To review, the problem is to solve 8 equations for 8 unknowns. The
unknowns are x[1],x[2],x[3],..,x[8] and the augmented matrix is,

AA1 AB1 AC1 ... AH1 | AI1
AA2 AB2 AC2 ... AH2 | AI2
AA3 AB3 AC3 ... AH3 | AI3
..
..
AA8 AB8 AC8 ... AH8 | AI8

What did I do wrong?

Jon

*** Sent via Devdex http://www.devdex.com ***
Don't just participate in USENET...get rewarded for it!
  #5   Report Post  
Old July 6th 04, 03:30 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2004
Posts: 2
Default solving a matrix in Excel

The augmented matrix

AA1 AB1 AC1 ... AH1 | AI1
AA2 AB2 AC2 ... AH2 | AI2
AA3 AB3 AC3 ... AH3 | AI3
..
..
AA8 AB8 AC8 ... AH8 | AI8

I attempted to solve with the two operations,

=MINVERSE(AA1:AH8) saved in AA11:AH18
=MMULT(AA11:AH18,AI1:AI8)

in Excel, but all I got was garbage. Some ove the cells were very
large (1E14). When I tediously solved the matrix using elementary row
operations, there was virtually no error. Did I do something wrong?

*** Sent via Devdex http://www.devdex.com ***
Don't just participate in USENET...get rewarded for it!


  #6   Report Post  
Old July 6th 04, 03:59 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Aug 2007
Posts: 783
Default solving a matrix in Excel

Dare wrote:

The augmented matrix

AA1 AB1 AC1 ... AH1 | AI1
AA2 AB2 AC2 ... AH2 | AI2
AA3 AB3 AC3 ... AH3 | AI3
.
.
AA8 AB8 AC8 ... AH8 | AI8

I attempted to solve with the two operations,

=MINVERSE(AA1:AH8) saved in AA11:AH18
=MMULT(AA11:AH18,AI1:AI8)

in Excel, but all I got was garbage. Some ove the cells were very
large (1E14). When I tediously solved the matrix using elementary row
operations, there was virtually no error. Did I do something wrong?

*** Sent via Devdex http://www.devdex.com ***
Don't just participate in USENET...get rewarded for it!

The methodology is correct; the solution vector should be given by

=MMULT(MINVERSE(AA1:AH8),AI1:AI8)

Perhaps you'd like to post the elements of the constituent matrices so
we can reproduce your problem. Excel is not always very good at
extracting the inverse when some of the results are very large or very
small.

Alan Beban
  #7   Report Post  
Old July 7th 04, 07:45 AM posted to microsoft.public.excel.programming
external usenet poster
 
First recorded activity by ExcelBanter: Jul 2004
Posts: 2
Default solving a matrix in Excel


reference of root:
(1,-1,1,-1,1,-1,1,-2)*X-1=0

below the data is 9 elements long per row, with the last element of the
row the augment of the matrix:

row 1:
-0.87618856 -0.287065453 -0.013432611 0.091462494 -0.013432611 0.0914624
94 -0.013432611 0.093827036 -0.090909091

row 2:
-0.287065453 -0.285522631 0.136657108 -0.147725177 0.136657108 -0.147725
177 0.136657108 -0.148060573 0.090909091

row 3:
-0.013432611 0.136657108 -0.77085744 0.12890946 0.22914256 0.12890946 0.
22914256 0.139759521 -0.090909091

row 4:
0.104037807 -0.147725177 0.12890946 -0.847780517 0.12890946 0.152219483
0.12890946 0.160738542 0.090909091

row 5:
-0.013432611 0.136657108 0.22914256 0.12890946 -0.77085744 0.12890946 0.
22914256 0.139759521 -0.090909091

row 6:
0.091462494 -0.147725177 0.12890946 0.152219483 0.12890946 -0.847780517
0.12890946 0.160738542 0.090909091

row 7:
-0.013432611 0.136657108 0.22914256 0.12890946 0.22914256 0.12890946 -0.
77085744 0.139759521 -0.090909091

row 8:
0.093827036 -0.148060573 0.139759521 0.160738542 0.139759521 0.160738542
0.139759521 -0.830155456 0.181818182

the nature of the problem is outlined on my site at,

http://mypeoplepc.com/members/jon8338/polynomial/

Jon

*** Sent via Devdex http://www.devdex.com ***
Don't just participate in USENET...get rewarded for it!


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Solving Sudoku using Excel azmanblues Excel Discussion (Misc queries) 5 July 28th 09 05:32 PM
Solving Sudoku with EXCEL LynnI via OfficeKB.com Excel Worksheet Functions 4 January 29th 08 03:40 AM
Mathematic problem solving using Excel Stonewall Excel Worksheet Functions 2 August 15th 06 08:16 PM
solving equations using Excel arnold_charming Excel Discussion (Misc queries) 0 December 7th 05 04:30 PM
i've got a simple excel problem that needs solving... Massive Excel Discussion (Misc queries) 6 May 16th 05 08:46 AM


All times are GMT +1. The time now is 01:04 PM.

Powered by vBulletin® Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2004-2017 ExcelBanter.
The comments are property of their posters.
 

About Us

"It's about Microsoft Excel"

 

Copyright © 2017