MATLAB: How to iterate until the difference between variable is equal to zero

iteration

tf = 140
V = (1.5800e-08)*exp((1.1575e+03)/(tf + 95))
S = (625)^2*((V*(N/60))/160)
delta_T = (0.349109 + (6.0094*S)+(0.047467*(S^2)))*(160)/9.7
t_ave = 120 + (delta_T/2)
tff = (tf + t_ave)/2
delta = tf-t_ave
while tf-t_ave >0
    tf = tff
    t_ave = 120 +(delta_T/2)
end
i want to make the value of tff as the new value for tf and keep on until tf and tff got the same value of number.

Best Answer

The iteration is not clear. You need to update the values of tf and t_ave inside the while loop. I guess that is an optimization problem and you want tf-t_ave = 0, and following your image I can see that tf is updated in each iteration by 
tf = tf - (tf-t_ave)/2
There aremore efficient options for optimization problems than this while loop, but the code that implements the iterations you have in the image is as follows:
tol = 1e-2;
tf = 140
N = 1.7501e+03;
V = (1.5800e-08)*exp((1.1575e+03)/(tf + 95))
S = (625)^2*((V*(N/60))/160)
delta_T = (0.349109 + (6.0094*S)+(0.047467*(S^2)))*(160)/9.7
t_ave = 120 + (delta_T/2)
% tff = (tf + t_ave)/2
while abs(tf-t_ave) > tol
    delta = (tf-t_ave)/2;
    tff = tf;
    tf = tf-delta
    
    V = (1.5800e-08)*exp((1.1575e+03)/(tf + 95));
    S = (625)^2*((V*(N/60))/160);
    delta_T = (0.349109 + (6.0094*S)+(0.047467*(S^2)))*(160)/9.7;
    t_ave = 120 + (delta_T/2)
end
Related Question