MATLAB: “Operands to the || and && operators must be convertible to logical scalar values” issue where those operators haven’t been used?? Potentially caused by vpaintegral.

||logical scalar valuesMATLABoperandsoperatorsvpaintegral

Hi, my code is throwing up the error shown below, can anyone help solve the cause of the issue?
Operands to the || and && operators must be convertible to logical scalar values.
Error in sym/vpaintegral (line 182)
   (isinf(b) && isempty(symvar(b)) && ~isreal(b))
Error in BASICscript (line 66)
        k_timedependant(i)=K_quasistatic(i)*(1.25*vpaintegral(sigma_prime(i),s,0,t(i)-tau)+vpaintegral(sigma_prime(i)*sqrt(t(i)-s),s,t(i)-tau,t(i)));
I can't quite figure out why as those operators arn't part of the code and I don't understand vpaintergral enough to know if that's the issue… It does seem to run two iterations before bowing out…
Any help would be much appreciated.
The code is as below,
    syms z s
    %Droplet properties
    r=0.001;                            % droplet radius (m)
    V=400;                              % impact velocity (m/s)
    rho=997;                            % at room temp (kg/m^3)
    Initial_c=30e-6
   
    %Glass properties
    pois=0.25;
    Beta=(1-2*pois)/2;
    K_IC=0.75e6;
    %Rayleigh Stress wave
    const=2;                            % Constant defined in interim report
    Co=1500;                            % Acoustic velocity(m/s)
    Cr=Co+(const*V);                    % Rayleigh wave velocity (m/s)
    sigma_max=rho*Cr*V*Beta;
    k=(2*pi*Initial_c^2)/(3*Cr*r*V);
    sigma_z=sigma_max*(exp(-0.8475*k*z)-0.5773*exp(-0.3933*k*z));
    v_max=1580;                         %maximum crack velcoity (m/s)
    
    %Triangular Wave 
    midpoint=(3*r*V)/(2*Cr^2);
    grad=sigma_max/midpoint;
   
    %Initialisation

    crack_growth=0
    
    final_t=3e-7;
    iterations=1000;
    t = [0:final_t/(iterations):final_t];
    for i = 1:iterations+1;
        %Calculation of Velocity Term 
        %Initialisation
        if i>1
            c(i)=c(i-1)
            v_inst(i)=0
            if v_inst(i-1)==0;
                k_velocity(i)=1;
            else
                k_velocity(i)=1/((1+(v_inst(i-1)/(Cr-v_inst(i-1))))*(1-((0.531*v_inst(i-1))/Cr))^0.5);
            end
        else
            k_velocity(i)=1;
            c(i)=Initial_c
        end
        
        %Sigma prime designation
        if t(i)>midpoint
            sigma_prime(i)=-(grad);
        else
            sigma_prime(i)=(grad);
        end    
        
        %Calculation of Quasi-Static and Time-Dependant Terms         
        funct(i)=(1-(z/c(i))^2)*(0.2945-0.3912*(z/c(i))^2+0.7685*(z/c(i))^4-0.9442*(z/c(i))^6+0.5094*(z/c(i))^8);
        K_quasistatic(i)=2*sqrt(c(i)/pi)*vpaintegral((sigma_z*(1+funct(i)))/sqrt(c(i)^2-z^2),z,0,c(i));
    
        tau(i)=((1.25^2*pi^2)*c(i))/(4*Cr);
        k_timedependant(i)=K_quasistatic(i)*(1.25*vpaintegral(sigma_prime(i),s,0,t(i)-tau)+vpaintegral(sigma_prime(i)*sqrt(t(i)-s),s,t(i)-tau,t(i)));       
        
        %Dynamic Stress intensity factor calculation
        K_D(i)=k_velocity(i)*K_quasistatic(i)*k_timedependant(i);
    
        %Stress intensity factor comaprision check
        if K_D(i)>K_IC
            %Crack Velcocity Calculation
            v_inst(i)=v_max*(1-(K_IC/K_D)^2);
            if i>1
                v_avg(i)=(v_inst(i)+v_inst(i-1)/2);
                crack_growth(i)=crack_growth(i)+(v_avg(i)*(t(i)-t(i-1)));
                c(i)=Initial_c+crack_growth(i);
            else
                v_avg(i)=0;
                crack_growth(i)=0;
                c(i)=Initial_c;
            end
        else
            v_avg(i)=0;
            crack_growth(i)=0
            c(i)=Initial_c;
        end
    end

Best Answer

        tau(i)=((1.25^2*pi^2)*c(i))/(4*Cr);
tau is a vector
      k_timedependant(i)=K_quasistatic(i)*(1.25*vpaintegral(sigma_prime(i),s,0,t(i)-tau)+vpaintegral(sigma_prime(i)*sqrt(t(i)-s),s,t(i)-tau,t(i)));
You are using the entire vector in building the upper bounds for integration. You should be using tau(i) instead of tau
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