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

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SITI AISHAH
SITI AISHAH 2019-3-28
评论： SITI AISHAH 2019-3-29
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.
  2 个评论
Alex Mcaulley
Alex Mcaulley 2019-3-28
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
SITI AISHAH 2019-3-28
编辑：SITI AISHAH 2019-3-28
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.

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采纳的回答

Alex Mcaulley
Alex Mcaulley 2019-3-29
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
  1 个评论
SITI AISHAH
SITI AISHAH 2019-3-29
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 :)

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