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SOE findroot question: is there an order for vars?
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Joined: 01/01/2022(UTC) Posts: 12 
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Hi, Guys: I'm using FindRoot for SOE solution,but something make me confusion. for example:  the same SOE with different variables, different result, and the second is wrong. I think maybe I have something wrong. please help me, how to use the FindRoot? Thanks a lot! John attach the file  soe.sm (7kb) downloaded 7 time(s).
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Joined: 28/08/2014(UTC) Posts: 1,478  Was thanked: 930 time(s) in 590 post(s)
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Hi. You must to sort the variables in the same order than Unknowns.  Best regards. Alvaro
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 1 user thanked Razonar for this useful post.
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Originally Posted by: Razonar  Hi. You must to sort the variables in the same order than Unknowns. Best regards. Alvaro Hi, is there any rules for the order?  Thanks alot John
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Rank: Advanced Member Groups: Registered
Joined: 28/08/2014(UTC) Posts: 1,478 Was thanked: 930 time(s) in 590 post(s)
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Hi. You can't redefine Unknowns. Well, you can, but isn't the best idea. Unknowns is a function in the same plugin than FindRoots, SpecialSolvers. I don't know the internals of the plugin. My guess that the general rule is sort the variable names in lexical order, but if the name has unicode characters or some unusual ASCII character, it is best to make sure of the order to follow by evaluating Unknows(eq).
Best regards.
Alvaro.
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okay， I got it. but a new question, why I can't got the result as your picture?  would you mind post the sample sm file ? Thanks a lot! John Edited by user 11 May 2022 11:33:01(UTC)
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Originally Posted by: johnpan okay， I got it. but a new question, why I can't got the result as your picture? SMath have two "=": Numerical and Symbolical. With numerical evaluation you can only obtain numerical values, that is, without undefined variables. Rigth click to change it to symbolic equals, or use Ctrl+period instead "=", or click symbolic evaluation in the right panel. Originally Posted by: johnpan
would you mind post the sample sm file ?
Sorry, I forgot to post it, and right now can't. Best regards. Alvaro.
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 thank you! I got it. Thanks a lot! John
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You can automate assigning guesses to unknowns. By this way, you won't care order of them. Regards findroot_auto.sm (5kb) downloaded 17 time(s).
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on 11/05/2022(UTC), on 12/05/2022(UTC)
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Originally Posted by: Jean Giraud For your example, make it algo style for local infinite use.
Observe ... sols:=U^-1*V is universal outside of Smath Plugin(s) ... your question about order of vars solutions are by convention in descending order of the pair wise u, v no matter the names you give. I can't explain the decimals difference between MCD 11/Smath. There are other constants that can't be found exactly ... Pitot constant, Goat radius constant ... That remark applies to any solvers [Smath and wrt any CAS] The U^1*V is the core component of the Cholesky solver as applied to fitting model function to a data set. In that case, best fit is obtained by iterating the Genfit. Chers ... Jean. 
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... here, you can push the cork in the bottle to accommodate irrational pi. as well ignore epsilon. 
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... as it looks, the max I could push the cork in the bottle
y≡0.279339266990994 ... sanity f(x,y,z)=-0.000000000001344
Confirms impossible exactly solving irrational numbers.
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Long word short, there is an order for vars.
You can either avoid it manually or automatically.
It is up to users choice which suits them most.
Either one has advantages over other.
Regards
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Thank you all so much! a nice forum 
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I never thought the time would come when I would become an expert at ignoring specific comments on a forum...thanks Jean! 
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Originally Posted by: johnpan Thank you all so much ! Solving is very important in Engineering Projects. Reserve ... solve, roots, FindRoots and more to specific applications Solving a square matrix goes via the conventional solver, no flaw. This didactic document has been refreshed. Cheers ... Jean. Solve Algebraic, MULTISOLVE DIDACTIC.sm (22kb) downloaded 14 time(s).
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Originally Posted by: churichuro I never thought the time would come when I would become an expert at ignoring specific comments on a forum.
...Thanks Jean! Many of the advanced Smath documents are join venture. Adapted/exemplified from various sources. Download: Samples, Utilities Most used_3. If something is not clear, please don't hesitate. You have more, please offer. Take care Amigo ... Jean.
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Joined: 23/07/2013(UTC) Posts: 1,173 Was thanked: 534 time(s) in 358 post(s)
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No churichruo, dont.
If you will post same worksheets 600 times, (satire here)
and then you will tease how less another one contributed,
and how your post statistic is 18.3% of entire forum,
Please don't.
You will just make a fool of yourself.
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1 user thanked overlord for this useful post.
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Originally Posted by: overlord No churichruo, dont.
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You will just make a fool of yourself. Do you mean churichruo will make a fool of himself from reputed contributors in this document: Mathsoft, Robert Adair, Carlos, Martin, Viacheslav, Romberg, Riemann FD, Hermite Polyline, Legendre, Gram_Schmidt, Guiseppe Borzi [simplex], Mathsoft Collaboratory Convolution ... I will add Fresnel [Clothoid]. churichruo wrote Tanks Jean
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