how to iterate until the difference between variable is equal to zero

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.

[Alex Mcaulley]

N is not defined. By the way, your while loop never finishes (tf - t_ave have allways the same value), unless

tf <= t_ave || tff <= t_ave

What do you exactly want to do? Because the answer to your question is trivial:

tf = t_ave
tff = t_ave

And no while loop is needed.

[SITI AISHAH]

hi alex, I want to do iteration as in the figure attached. I want to stop the iteration once the difference between tf and t_ave had become 0. I also want to make tff value as the new tf and keep iterate until both of them got the same number and that will make difference between tf and t_average as 0. btw , tf > t_average and that's why i want to iterate until they become 0.

Answer 1

[Alex Mcaulley]

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

[SITI AISHAH]

Hi Alex. This is such a big help for me. I've tried your code and its working. Thank you so much. I appreciate it as I'm new in using MATLAB. Thanks again :)