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

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Marcelin Dierickx
Marcelin Dierickx 2018-12-28
评论： Marcelin Dierickx 2018-12-29
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.

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采纳的回答

Walter Roberson
Walter Roberson 2018-12-28
You cannot use symbolic variables in the bounds.
You can add constraints as expressions to be solved for.

更多回答（1 个）

madhan ravi
madhan ravi 2018-12-28
编辑：madhan ravi 2018-12-28
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
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madhan ravi
madhan ravi 2018-12-29
编辑：madhan ravi 2018-12-29
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.

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