Warning: Explicit solution could not be found. > In solve at 81 - Symbolic Math Toolbox

2011 5 21
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These are the equations:
X1_1 + X2_1 - 23687/100
X1_2 + X2_2 - 4980831654290391/4398046511104
X1_3 + X2_3 - 40309/25
X1_4 + X2_4 - 7701/10
X1_5 + X2_5 - 10829/25
2*(X1_1/2 - X2_1/2)^2 - 4050288284713621/4398046511104
2*(X1_2/2 - X2_2/2)^2 - 6817447548526841/274877906944
2*(X1_3/2 - X2_3/2)^2 - 4273253568628633/137438953472
X1_1 + X1_2 + X1_3 + X1_4 + X1_5 - 3489233779827237/2199023255552
X2_1 + X2_2 + X2_3 + X2_4 + X2_5 - 5713678544657883/2199023255552
Does this system has valid solutions OR Matlab is not able to find them?

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Andrew Newell
Andrew Newell 2011-5-21
This looks like a system that the toolbox should solve easily. What command did you use to solve it?
condor
condor 2011-5-21
Solutions=solve(Tequazioni);
In Tequazioni I have all the equations
Daniel Shub
Daniel Shub 2011-5-21
Can you post some code that can be cut and pasted into the command window to recreate the error. Including you solve method, and how you define Tequazioni.

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Walter Roberson
Walter Roberson 2011-5-21

1 个投票

There is indeed no solution.
The 4th line says X1_4 = constant1 - X2_4
The 5th line says X1_5 = constant2 - X2_5
The 9th line has X1_4 + X1_5 so that is going to be constant1 + constant 2 - (X2_4 + X2_5)
The 10th line has X2_4 + X2_5 .
Everything else on line 9 and line 10 can be resolved down to explicit values by way of the previous lines (lines 1-3 and 6-8)
Add substituted line 9 to line 10; because one has +(X2_4+X2_5) and the other has -(X2_4+X2_5) the X2_4 and X2_5 will cancel out leaving a constant sum. If that constant sum is not equal to 0 then the system has no solutions. The constant sum does indeed not equal to 0.

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condor
condor 2011-5-21

0 个投票

Please consider this code:
tic
display('Computing...');
drawnow;
load DATI(2)_test
variabili=sym('X', [2 5]);
variabili=sym(variabili, 'positive');
%FORMULA GENERALE CALCOLO MEDIA-VARIANZA
syms n i
Xi = sym('X[i]');
mean = symsum(Xi,i,1,n)/n;
variance = symsum((Xi-mean)^2,i,1,n);
b=2;
variance_b = subs(variance,n,b);
Xb = arrayfun( @(x) sprintf( 'X[%d]', x ), 1:b, 'UniformOutput', false ); % Cell array of vector - Gruppo 2
for j=1:5
%5 equazioni - SOMMA COLONNE (ogni riga corrisponde ad un gruppo)
equaz.SommaColonne(1,j)=sum(variabili(1:2,j))-SommaColonne(1,j);
end
for u=1:3
%3 equazioni - VARIANZA COLONNE (ogni riga corrisponde ad un gruppo)
equaz.VarianzaColonne(1,u)=subs(variance_b,Xb,variabili(1:2,u))-VarianzaColonne(1,u);
end
%2 equazioni - SOMMA RIGHE (ogni riga corrisponde ad un gruppo)
equaz.SommaRighe(1,1)=sum(variabili(1,1:5))-SommaRighe(1,1);
equaz.SommaRighe(2,1)=sum(variabili(2,1:5))-SommaRighe(2,1);
RSommaColonne=reshape(equaz.SommaColonne,5,1);
RVarianzaColonne=reshape(equaz.VarianzaColonne,3,1);
Tequazioni=[RSommaColonne' RVarianzaColonne' equaz.SommaRighe']';
Soluzioni=solve(Tequazioni);
toc
DATI(2)_test.mat CAN BE DOWNLOADED HERE: http://www.speedyshare.com/files/28573299/DATI_2_test.mat

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