struggling with error in code

Hi all I am trying to run the code below and get an error i do not know what means.

clear all 
close all
clc

Vo = linspace(5,25,41);
lambda = 7.5;
beta=(0:8:0.5);
r=27.46;
R = 30.56;
B = 3;
rho = 1.225;
omega = 2.0;
Vcutin = 5;
Vcutout = 25;
ratedP = 2500000;
alpha=4;
c=0.1:0.1:3;
%%Initializing Data
old_a = 0;
old_a_prime = 0;
a = 0;
a_prime = 0;
ac = 1/3;
corr = 0.1;
tolerance = 0.001;

%%BEM Iterations
while (((abs(old_a-a) > tolerance) || (abs(old_a_prime-a_prime) > tolerance)) || (a == 0))
    old_a = a;
    old_a_prime = a_prime;    

      phi = atan((1-a)*R/((1+a_prime)*lambda*r));
      phideg = phi*180/pi;
      theta=phideg-alpha;

      Cl = 0.8; 
      Cd=0.012;

      Cn = Cl*cos(phi) + Cd*sin(phi);
      Ct = Cl*sin(phi) - Cd*cos(phi);

      F_new=(2/pi)*acos(exp(-(B/2)*(R-r/r*sin(phi))));
      sigma=c.*B/(2*pi*r);  %solidity

      %Tip loss correction
      f = B*(R-r)/(2*r*sin(phi));
      F = 2*acos(exp(-f))/pi;

      %Glauert correction for high 'a' value
      if(a > ac)
        CT = (1-a)^2 * Cn*sigma/(sin(phi)^2);
        a_star = a - (4*a*(1-0.25*(5-3*a)*a)-(CT/F))/(9*(a^2)-10*a+4);
        a = corr*a_star + (1-corr)*a;
      else
        a = 1./((4*F*(sin(phi)^2)./(sigma'*Cn))+1);
      end
      a_prime = 1./((4*F*(sin(phi)^2)*cos(phi)./(sigma'*Ct))-1);
  end
  for i=0.1:0.1:3
  Cp_local=(B*lambda^2*(r/R)*(1-a)*(1+a_prime)*(c(i)/R)*Ct/(2*pi*sind(phi)*cosd(phi)));
  end

Operands to the || and && operators must be convertible to logical scalar values.

Error in question7 (line 28)
while (((abs(old_a-a) > tolerance) || (abs(old_a_prime-a_prime) > tolerance)) || (a == 0))

[per isakson]

Your code make me think that all the variables in the logical expressions in while expression are supposed to be scalars.

However,

        if(a > ac)
            CT = (1-a)^2 * Cn*sigma/(sin(phi)^2);
            a_star = a - (4*a*(1-0.25*(5-3*a)*a)-(CT/F))/(9*(a^2)-10*a+4);
            a = corr*a_star + (1-corr)*a;
        else
            a = 1./((4*F*(sin(phi)^2)./(sigma'*Cn))+1);
        end

turns a into a vector, which in turn causes the error.

[per isakson]

"struggling" Don't you use the debugging features? See Debug a MATLAB Program

Answer 1

[Jyotish Robin]

Hi Casper!

This error is seen if the operands being evaluated by the short-circuit and && operators are empty or non-scalar arrays. Use the logical and (&), or (|) operators for non-scalar operands.

Refer to the link below for information on logical operators.

and, & :

http://www.mathworks.com/help/matlab/ref/and.html

or, | :

http://www.mathworks.com/help/matlab/ref/or.html

There are some ML Answers posts which discuss similar queries. You can have a look at the following:

• https://www.mathworks.com/matlabcentral/answers/77558-how-to-solve-this-error-operands-to-the-and-operators-must-be-convertible-to-logical-scalar-v
• https://www.mathworks.com/matlabcentral/answers/143576-operands-to-the-and-operators-must-be-convertible-to-logical-scalar-values

I hope the above suggestions will be helpful.

Thanks,

Jyotish