Matlab problem with using the "solve" function for Algebraic equations

[doreen105]

Hi everyone:
I have met problem when I use function 'solve" to solve Algebraic equations.

The warning is: explicit solution could not be found

In solve at 140

result=[empty sym]

Can any one help me???Thanks in advance.

 

[standup]

Re: Matlab problem

can you specify it?
what's the source program?[/quote]

 

[hazemafify]

Re: Matlab problem

can you put the program that you wrote but any way you can make help about solve function in matlap and you can get the correct syntax .
i thank that this function is used with symbolic equations.

 

[pareshatlnmiit]

Re: Matlab problem

Look I have got the same error while integrating some function ,so if you can show me your equations i can suggest you the way

 

[doreen105]

Re: Matlab problem

This is my code:
syms a1 a2 a3 a4 a5 g1 g2 g3 g4 g5 b1 b2 H z;

y=sym('(1-b1*(H^2)*g2*g3)*(1-b2*(H^2)*g4*g5)+H*g1*a1*(1-b1*(H^2)*g2*g3)*(1-b2*(H^2)*g4*g5)+(H^2)*g1*g2*a2*(1-b2*(H^2)*g4*g5)+H^3*g1*g2*g3*a3*(1-b2*(H^2)*g4*g5)+H^4*g1*g2*g3*g4*a4+H^5*g1*g2*g3*g4*g5*a5');

fm=collect(y,'H')

x=sym('(1-b1*(H^2)*g2*g3)*(1-b2*(H^2)*g4*g5)');

fz=collect(x,'H')

fm1=sym('(z-1)^5+(g1*a1*b1*g2*g3*b2*g4*g5-g1*g2*g3*a3*b2*g4*g5+g1*g2*g3*g4*g5*a5)*1+(b1*g2*g3*b2*g4*g5-g1*g2*a2*b2*g4*g5+g1*g2*g3*g4*a4)*(z-1)+(-g1*a1*b2*g4*g5-g1*a1*b1*g2*g3+g1*g2*g3*a3)*(z-1)^2+(-b2*g4*g5-b1*g2*g3+g1*g2*a2)*(z-1)^3+g1*a1*(z-1)^4')

fz1=sym('(z-1)^5+b1*g2*g3*b2*g4*g5*(z-1)+(-b2*g4*g5-b1*g2*g3)*(z-1)^3')

fz2=collect(fz1,'z')

fm2=collect(fm1,'z')

[B,A]=butter(5,0.5,'high')

B=B*18.9394*1.0003

A=A

[H,F]=freqz(B,A,100);

Hf=abs(H);

Hx=angle(H);

plot(F,Hf)

result=solve('10-b2*g4*g5-b1*g2*g3=B(3)','-10+3*b2*g4*g5+3*b1*g2*g3=B(4)','5+b1*g2*g3*b2*g4*g5-3*b2*g4*g5-3*b1*g2*g3= B(5) ','-1-b1*g2*g3*b2*g4*g5+b1*g2*g3+b2*g4*g5= B(6)','g1*a1-5=A(2)','-b1*g2*g3-b2*g4*g5-4*g1*a1+10+g1*g2*a2=A(3)','3*b2*g4*g5-3*g1*g2*a2+g1*g2*g3*a3+6*g1*a1-g1*a1*b2*g4*g5-g1*a1*b1*g2*g3+3*b1*g2*g3-10=A(4)','-3*b2*g4*g5+2*g1*a1*b2*g4*g5+3*g1*g2*a2-g1*g2*a2*b2*g4*g5+5-4*g1*a1+b1*g2*g3*b2*g4*g5+2*g1*a1*b1*g2*g3-2*g1*g2*g3*a3-3*b1*g2*g3+g1*g2*g3*g4*a4=A(5)','-1-g1*g2*a2+b1*g2*g3-b1*g2*g3*b2*g4*g5-g1*a1*b1*g2*g3-g1*a1*b2*g4*g5+g1*a1*b1*g2*g3*b2*g4*g5+b2*g4*g5-g1*g2*g3*a3*b2*g4*g5-g1*g2*g3*g4*a4+g1*g2*g3*g4*g5*a5+g1*g2*g3*a3+g1*g2*a2*b2*g4*g5+g1*a1=A(6)','a1','a2','a3','a4','g1','g2','g3','g4','g5')


my code is to caculate the coefficients of my digital system...

Thanks in advance

 

[tantoun2004]

Re: Matlab problem

Hi,
I think that the error you get is due to that you didn't install the symbolic math toolbox or the extended math toolbox. This i ssolved nby installing them from the MatLab source.
Hope this helps,

 

[wellgood]

Re: Matlab problem

Every freshman/woman:
I just run successfully some commands in delsig toolbox. There is at least a necessary step not mentioned above, that is search path setting. Please enter menu File-- Set Path...--Add Folder...--, then browse into the target toolbox path where you have put it.(e.g. C:\MATLAB7\toolbox\delsig\delsig).

enjoy it!