From: SourceForge.net <noreply@so...>  20070131 08:50:25

Bugs item #1521112, was opened at 20060712 04:14 Message generated for change (Comment added) made by nobody You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1521112&group_id=4933 Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Lisp Core  Solving equations Group: None Status: Open Resolution: None Priority: 5 Private: No Submitted By: Araceli Gárate García (agarate) Assigned to: Nobody/Anonymous (nobody) Summary: To know which are the inconsistent equations Initial Comment: Hi, I have an inconsistent equation system, I need to know which are the inconsistent equations when the linsolve command is used. I know that this is displayed when the flag solve_inconsistent_error is true, but I need to use this information in a program. For example, (%i169) linsolve([a+b=0,a+b=1,a+c=2],[a,c]); Inconsistent equations: (2)  an error. Quitting. To debug this try debugmode(true); (%i170) I need to know that 2 is the inconsistent equation, Is there any way to know that? Thank you Araceli  Comment By: Nobody/Anonymous (nobody) Date: 20070131 00:50 Message: Logged In: NO hi (%i12) linsolve([a+b=1,a+c=2],[a,c]); (%o12) [a = 1  b, c = b + 1] (%i13) linsolve([a+b=0,a+c=2],[a,c]); (%o13) [a =  b, c = b + 2] (%i14) linsolve([a+b=0,a+b=1],[a,c]); Inconsistent equations: (2)  an error. To debug this try debugmode(true); the equations [a+b=0,a+b=1] are contradictory, and if you remove one of them your system has a solution. but look at the system linsolve([a=0,c=0,a+c=1],[a,c]) these three equations are inconsistent but if you pick two of them a unique solution exists. so what are the inconsistent equations? in the common case you cannot say these equations of a systems are inconsistent and the rest is consistent. of course an inconsistent system can contain an inconsistent subsystems, but i think how to find out such inconsistent subsystems is a question for a mathematics group and not for a bug report guenter  Comment By: Barton Willis (willisbl) Date: 20060813 19:53 Message: Logged In: YES user_id=895922 Without hacking the function solvex (in src/solve), I don't think there is a way to get at this information. Of course, which equation is is inconsistent is somewhat arbitrary: in [x=3,x=6,x=7], which two equations are inconsistent? Maybe you would like to use the function rank: (%i24) load(linearalgebra)$ (%i25) rank(matrix([6,7],[6,17])); (%o25) 2(%i26) rank(matrix([6,7],[6,7])); (%o26) 1  You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=104933&aid=1521112&group_id=4933 