MATLAB: When I assign x(n)=0.5 and x(n-1)=0.055 they are gathered into one vector? as x=[0.5 0.055]

newton raphson

I am doing a code for Newton-Raphson using Secant method as well. However, I should guess two values! How can I do that? you can see the attachment for my code. Please help if you can.

Best Answer

You might as well use rand() for the initial guesses, unless you have physical knowledge that would suggest other values.
You are going to need to change your code. You have
f(x(n))=((-(100-DOT(i)))/(100))+(1/(x(n)-60))*(x(n)*exp(-Time(i)/x1)-60*exp(-Time(i)/60))
for i=1:43
    while abs((f(x1)))>0.001
            x(n+1)=x(n)-((x(n)-x(n-1)))*(f(x(n))/(f(x(n))-f(x(n-1))))
            x0=x1;
            x1=x2;
            n=n+1;
    end
end
which tries to define a formula for f(x(n)) based upon general n and i values. The only way to define a formula is with the Symbolic Toolbox, and symbolic formulas need to be define in terms of variables rather than array elements.
Adjusted code:
x1 = nan;      %we do not know what this variable is for or how it should be initialized

x2 = nan;      %we do not know what this variable is for or how it should be initialized
for i=1:43
  f = @(X, X1) ((-(100-DOT(i)))/(100))+(1/(X-60))*(X*exp(-Time(i)/X1)-60*exp(-Time(i)/60));
      while abs((f(x(n), x1)))>0.001
              x(n+1) = x(n)-((x(n) - x(n-1))) * (f(x(n), x1) / (f(x(n),x1) - f(x(n-1),x1)));
              x0=x1;
              x1=x2;
              n=n+1;
      end
  end
This adjusted code is unlikely to work, as I see errors in your formula, but it will at least pass syntax checking.
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