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

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?

[Andrew Newell]

This looks like a system that the toolbox should solve easily. What command did you use to solve it?

[condor]

Solutions=solve(Tequazioni);

In Tequazioni I have all the equations

[Daniel Shub]

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.

[condor]

look below

Answer 1

[Walter Roberson]

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.

[condor]

yes you are right ... I didn't check the equations...

Answer 2

[condor]

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