I not able to understand what type error I am making in the while loop

I want to use babyloniansqrt to work if Error value should be grater than threshold and this will update the x and E value, using xnext = (x+S./x)/2, E = abs(S-xnext.^2) formula. Please check my code and let me know what I am doing wrong

function out = babyloniansqrt(S,threshold)
x = 1;
if ~exist('threshold','var')
	threshold = 0.00001;
end
E = abs(S-x.^2);
while ~(E<threshold)
	xnext = (x+S./x)/2;
	E = abs(S-xnext.^2);
end

Answer 1

[Rik]

You aren't updating the value itself, so the calculation is the exact same on every iteration.

function out = babyloniansqrt(S,threshold)
%Write lead line here
%
% write usage instructions and explanation here

x = 1;
if nargin<2
    %set default threshold if not provided
	threshold = 10^-5;
end

E = inf; %set initial value to enter the loop
while E>threshold
	x = (x+S./x)/2;
	E = abs(S-x.^2);
end
out=x;
end

[Manav Divekar]

this is not working as i have to E = abs(S-x.^2); to enter the loop

[Jan]

Change "E = abs(S-xnext.^2);" to "E = abs(S-x.^2);" in Rik's code.

[Rik]

Thanks for the correction Jan, I have edited my answer.