Index exceeds array bounds

Rho = 997;

g = 9.8;

Le =115.25 ;

Ae =214.4 ;

Ac =51.5 ;

Li =172;

Ai =84.13;

Di = (Ae/Ac)^2 - 1;

S = Ac;

beta2 = 14.3*(%pi/180);

w=92.3*(2*%pi)/60;

R=4;

U2 = w*R;

Head=114;

alfa = 1.3;

zt2 = 0.29;

ztT=34.47;

Qm=740;

  n=20;
  Xv=logspace(0,3,n)*1e-3;
  Cv=logspace(0,4,n)*1e-6;
  Sol=zeros(2,n);
  %%%%
  Cav = 0;
  for h=1:n
  X=-Xv(h);
  for i=1:n
  Cc=Cv(i);
  Eq=(Rho*Qm*(zt2-Di)/Ae^2)-((y^2)*Rho*X*(Li/Ai))-(Rho*Qm*(ztT/Ai^2))+Cc*(2*Rho^2*(y^2)*((cot(beta2))/S)*(((cot(beta2))/S)*Qm-U2)*(Le/Ae)+Rho^2*(Li/Ai)*(y^2)*Qm*((Di-zt2)/Ae^2)-(y^2)*(Rho^2)*(Le/Ae)*(ztT/Ai^2)*Qm)+Cav*(2*(Rho^2)*(y^2)*((cot(beta2))/S)*(((cot(beta2))/S)*Qm-U2)*(Le/Ae)+(Rho^2)*(Li/Ai)*(y^2)*Qm*((Di-zt2)/Ae^2)-(y^2)*(Rho^2)*(Le/Ae)*(ztT/Ai^2)*Qm); %%EQUAÇÃO CARACTERÍSTICA
  Sol(:,i)=double(vpasolve(Eq,y)); % SOLUÇÃO DA EQ. CARACTERÍSTICA
  Wr(h,i)= Eq(Sol(2,i));

I need to apply the result i get from vpasolve back in Eq so I can determinate if Wr is positive or negative and plot a graphic with it.

I am trying to plot a graphic with the solution, however in the last line I always get "Index exceeds array bounds"

[Adam]

Is there any guarantee that the result of a vpasolve of an equation will be a valid index into the Eq variable? It seems unlikely, but I don't use vpasolve so I wouldn't really know.

[Bob Thompson]

What are the sizes of Eq, and Sol, and the value of i when it errors?

[madhan ravi]

upload all the missing datas

[Alysson Guimarães]

The size of Eq is 1x1, Sol is 2x20 and i errors with value 1. I am no sure about guarantees, I am using vpasolve because it was used in a similar code, but is was a complex cubic equation.

I can not upload the data here, sorry.

[Adam]

You are using the result of this complex cubic equation to index into a scalar though. This makes no sense! I don't know what you are attempting to do with

Eq( Sol(2,i) )

but since Eq is a scalar then unless Sol(2,i) evaluates to 1 every time (in which case it is pointless) then it will error.

Answer 1

[madhan ravi]

EDITED

syms y

Rho = 997;

g = 9.8;

Le =115.25 ;

Ae =214.4 ;

Ac =51.5 ;

Li =172;

Ai =84.13;

Di = (Ae/Ac)^2 - 1;

S = Ac;

beta2 = 14.3*(pi/180);

w=92.3*(2*pi)/60;

R=4;

U2 = w*R;

Head=114;

alfa = 1.3;

zt2 = 0.29;

ztT=34.47;

Qm=740;

    n=20;
    Xv=logspace(0,3,n)*1e-3;
    Cv=logspace(0,4,n)*1e-6;
    Sol={zeros(1,n)}
    %%%%
    Cav = 0;
    for h=1:n
    X=-Xv(h);
    for i=1:n
    Cc=Cv(i);
    Eq=(Rho*Qm*(zt2-Di)/Ae^2)-((y^2)*Rho*X*(Li/Ai))-(Rho*Qm*(ztT/Ai^2))+Cc*(2*Rho^2*(y^2)*((cot(beta2))/S)*(((cot(beta2))/S)*Qm-U2)*(Le/Ae)+Rho^2*(Li/Ai)*(y^2)*Qm*((Di-zt2)/Ae^2)-(y^2)*(Rho^2)*(Le/Ae)*(ztT/Ai^2)*Qm)+Cav*(2*(Rho^2)*(y^2)*((cot(beta2))/S)*(((cot(beta2))/S)*Qm-U2)*(Le/Ae)+(Rho^2)*(Li/Ai)*(y^2)*Qm*((Di-zt2)/Ae^2)-(y^2)*(Rho^2)*(Le/Ae)*(ztT/Ai^2)*Qm); %%EQUAÇÃO CARACTERÍSTICA
    Sol{i}=double(vpasolve(Eq,y)); % SOLUÇÃO DA EQ.

    end
    end

celldisp(Sol) %this will display all the solutions you need :)

Sol=cell2mat(Sol) %to use for further calculations 

   Wr = vpa(subs({Eq},{Sol}))

[Alysson Guimarães]

How do I apply the result back in Eq? I tried using this code, but shows errors.

"Array indices must be positive integers or logical values

Error in sym/subsref (859)

        R_tilde = builtin('subsref', L_tilde. Idx);

Error in Rotina

     Wr(h,i) = Eq(Sol);

[madhan ravi]

see edited now

Answer 2

[Jan]

If Eq is a scalar, a 1x1 array, than the only working value of Sol(2,i) is 1. Otherwise Eq(Sol(2,i)) must fail, of course.

We cannot run the code due to the missing data, and cannot guess, what the code should do due to the lack of comments and explanations. It is not clear which variables are symbolic and which are numerical. Maybe you have redefined cot as an array?

[Alysson Guimarães]

The only symbolic is y. I uploaded the data if it helps.