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#1




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




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




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




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




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




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




solving a matrix in Excel
reference of root: (1,1,1,1,1,1,1,2)*X1=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! 
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