While Loop exiting before statement is met

Hi guys,

I have written a function which uses two vectors (221x1) . I now want to loop through each component until the residual is < 1e-4. However, the following code exits the while loop after the first iteration.

Could someone help out please?

function [alpha, PM]= alphacorrect(N,alpha_34,p)

K= 0.05315;
T= -0.00289;
c_deflect_vst=0.38;
dist_mrc=0.5;
PM=0;
alpha=0;

for i=1:length(N)
    
    delta_alpha=1;
    
    
    while delta_alpha> 1e-4

    alpha_cos=(alpha*pi)/180;
    
    dtheta=(N(i)*dist_mrc + PM).*K + N(i)*T -c_deflect_vst*cos(alpha_cos);
    
    if N(i)<0
        delta_alpha=alpha_34(i)-dtheta-alpha;
    else
       delta_alpha=alpha_34(i)+dtheta-alpha;
    end
    
    alpha=alpha_34(i)-dtheta;
    %PM= polyval(p,alpha);
    
    
    end
    i=i+1;
%     alpha(i)=alpha;
%    PM(i)=PM; 
end
end

[Torsten]

Why do you set i = i+1 after the while loop ?

[Jyothis Gireesh]

I tried to replicate the condition that you mentioned in the question using some random inputs. But in most of the cases, the value of delta_alpha turned out to be negative after the first iteration of while loop. Even in the other cases the program was executing normally.

Can you provide the values for “N” and “alpha_34” so that I may able to replicate the error?

[Aquatris]

Maybe you meant to use absolute value of delta_alpha as your while loop condition?