Sym: The second argument must be a vector of symbolic variables

This code:

R = 9 ; T = 300 ; g = 10 ;

syms h p Mm q m v b a f

F = (sqrt((h*(g*(q*(a+v)-m+((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)*(R*T*q/2*(1/p+1/(p+q*g*h))-Mm))-2*f))^2+4*(R*T*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)*log(R*T*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)/(p*((Mm*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)+m)/q-v-a))))^2)-h*(g*(q*(a+v)-m+((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)*(R*T*q/2*(1/p+1/(p+q*g*h))-Mm))-2*f))/(2*R*T*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)*log(R*T*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)/(p*((Mm*((m-q*v)/(R*T/(p/q+g*h)-Mm)+b)+m)/q-v-a)))) ;

dF_h = diff(F,h);
dF_p = diff(F,p);
dF_Mm = diff(F,Mm);
dF_q = diff(F,q);
dF_m = diff(F,m);
dF_v = diff(F,v);
dF_b = diff(F,b);
dF_a = diff(F,a);
dF_f = diff(F,f);

[Sh,Sp,SMm,Sq,Sm,Sv,Sb,Sa,Sf] = vpasolve([dF_h==0,dF_p==0,dF_Mm==0,dF_q==0,dF_m==0,dF_v==0,dF_b==0,dF_a==0,dF_f==0],[h,p,Mm,q,m,v,b,a,f],[0 Inf;30000 Inf;2 300;p/(R*T/Mm-g*h) 10000;0 Inf;0 m/q;0 Inf;0 Inf;0 Inf],'Random',true);

Gives me error:

Error using
sym.getEqnsVars>checkVariables (line 92)
The second argument must be a
vector of symbolic variables.

Error in sym.getEqnsVars (line 54)
    checkVariables(vars);

Error in sym/vpasolve (line 132)
    [eqns,vars] =
   sym.getEqnsVars(varargin{1:N});
    
Error in Rendement (line 17)
[Sh,Sp,SMm,Sq,Sm,Sv,Sb,Sa,Sf] = vpasolve([dF_h==0;dF_p==0;dF_Mm==0;dF_q==0;dF_m==0;dF_v==0;dF_b==0;dF_a==0;dF_f==0],[h;p;Mm;q;m;v;b;a;f],[0 Inf;30000 Inf;2 300;p/(R*T/Mm-g*h) 10000;0 Inf;0 m/q;0 Inf;0 Inf;0 Inf],'Random',true);

And I don't get why.

The equation is long, no real need to read them.

Thank you for answering.

Answer 1

[Walter Roberson]

You cannot use symbolic variables in the bounds.

You can add constraints as expressions to be solved for.

[Marcelin Dierickx]

Not showing me errors anymore indeed, gotta calculate for some hours now !

Thank you :-)

Answer 2

[madhan ravi]

doc vpasolve % read the right usage of it
[Sh,Sp,SMm,Sq,Sm,Sv,Sb,Sa,Sf] = vpasolve([dF_h==0,dF_p==0,dF_Mm==0,dF_q==0,dF_m==0,dF_v==0,dF_b==0,dF_a==0,dF_f==0],[h,p,Mm,q,m,v,b,a,f]); % only this the others after f]... I don't know why you have added 

[Marcelin Dierickx]

I added following informations from here:

vpasolve

It says in "Input Arguments > init guess" (bottom of the page) that you can write the initial values of variables as a matrix of 2 columns, one row per variable, 1st column beginning value and 2nd ending value, and in "Find multiple solutions for nonpolynomial equations" that " 'Random', true " can be used in conjunction with a search range

[madhan ravi]

well you are right buddy but then it’s mentioned no where that the init_guess should be symbolic I can see in two places p/(...) and m/q are symbolic variables which is leading to error.

[Marcelin Dierickx]

Yeah that was it thank you :-)