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Make an while-loop stop when conditions is fullfilled

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Helene Andersen
Helene Andersen 2016-5-12
编辑： Weird Rando 2016-5-12
First of all I am new to MATlab, but I have made this code for Newton's method. My problem is that I have said that the code should make 100 iteration, but I want it to stop when it converges. How can I do this?

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回答（2 个）

Walter Roberson
Walter Roberson 2016-5-12
if convergence_test_goes_here
break;
end
for example,
if abs(fx - prev_fx) < 1E-10
break
end
Weird Rando
Weird Rando 2016-5-12
编辑：Weird Rando 2016-5-12
Just use an AND logic '&' to identify both condition for the while loop.
clc
clear
%%Website
%f(x) = x^3 - x + 1 = 0
%f'(x) = 3x^2 - 1
% The root of the function is between -1 and -2
x = -2:0.1:2;
y = x.^3 - x + 1;
plot(x,y)
grid on
%%Example
counter = 0;
converge = -1.3247;
x1 = -1; %initial guess
while counter < 100 & round(x1*10000)/10000 ~= converge
x1 = x1 - (x1^3 - x1 + 1)/(3*x1^2 - 1)
counter = counter + 1;
end
(source: http://www.ugrad.math.ubc.ca/coursedoc/math100/notes/approx/newton.html)

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