Calculate with initial value

i=1;
Z(i)=1;
while true 
    Z(i) =1 + B - q.*B.*(((Z(i))-B)./(((Z(i))-B*sigma)*((Z(i))+epsi*B)))-Z(i); 
    i=i+1;
end

[Sulaymon Eshkabilov]

Note that in your set up "while" loop, Z(i) can't be on both sides of the equal sign. Z(i) on the left side has to be Z(i+1).

Answer 1

[per isakson]

There is nothing that terminates the execution of the loop when convergence is reached. Thus, the while-loop will run until the vector, Z, exceeds "Maximum possible array" or something else throws an error.

i=1;
Z(i)=1;
while true
    Z(i+1) = 1 + B - q.*B.*(((Z(i))-B)./(((Z(i))-B*sigma)*((Z(i))+epsi*B)));
    i = i+1;
end

Replace the loop by

tol = 1e-6;
i = 2;
Z(i)   = 1;
Z(i-1) = Z(i)+2*tol;
while abs(Z(i)-Z(i-1)) >= tol
    Z(i+1) = 1 + B - q.*B.*(((Z(i))-B)./(((Z(i))-B*sigma)*((Z(i))+epsi*B)));
    i = i+1;
end

[Jamil Arif]

Z(i-1) = Z(i)+2*tol;

what is the function for this part of the eqn

[per isakson]

The purpose of

Z(i-1) = Z(i)+2*tol;

is to make sure that

abs(Z(i)-Z(i-1)) >= tol

returns true and thus that the statements in the while-loop are executed for i equal to 2. Try to execute the code without it.