I think the problem is that you're checking the condition t > R at a fixed position in your loop, but you don't know beforehand which iteration i will satisfy this condition when you change the vector sizes or the value of R.
The solution is to break out of the loop as soon as the condition t > R is met, rather than continuing to iterate through all elements. Here's a modified version of your code:
A=zeros(10,1);
x=zeros(10,1);
C_N=zeros(10,1);
R=3.303;
r=1;
x(1)=0;%2*r*sind(acosd((R-r)/(2*r*(fix(R)-1))));
A(1)=R;
C_N(1)=fix(R/r);
for i=2:numel(A)
x(i)=2*r*sind(acosd((A(i-1)-r)/(2*r*(fix(A(i-1)/r)-1))));
A(i)=R*sind(acosd(sum(x)/R));
C_N(i)=2*fix(A(i)/r);
t=sum(x);
if t>R
A(i)=0;
x(i)=0;
C_N(i)=0;
% Use A(i-1) which contains the previous valid value
k0=0.5*A(i-1);
k1=k0-fix(k0);
Km=[1:1:fix(0.5*A(i-1))]';
if k1==0
for j=1:numel(Km)
corr(j)=2*fix(2*(sqrt(R^2-(Km(j)*r+0.18)^2)-sum(x))/r);
if j==numel(Km) && corr(j)<1 && numel(Km)==2
corr(j)=fix(2*(sqrt(R^2-(0)^2)-sum(x))/r);
C_Ncorr=sum(corr);
C_N(i-1)=C_Ncorr;
elseif j==numel(Km)
C_Ncorr=sum(corr);
disp(C_Ncorr);
C_N(i-1)=C_Ncorr;
end
end
else
for j=1:numel(Km)
corr(j)=2*fix(2*(sqrt(R^2-(2*Km(j)*r+0.36)^2)-sum(x))/r);
if j==numel(Km)
corrlast=fix(2*(sqrt(R^2-(0)^2)-sum(x))/r);
C_Ncorr=sum(corr)+corrlast;
C_N(i-1)=C_Ncorr;
end
end
end
% Break out of the main loop once condition is met
break;
end
% display(C_N(1:i));
end
% Display results
fprintf('Final k0 value: %.3f\n', k0);
fprintf('Km matrix:\n');
disp(Km);
fprintf('Valid entries in A: %d\n', sum(A~=0));
fprintf('A values:\n');
disp(A(A~=0));
