Newton-Raphson with polyvals and polyder

Hello,

I am trying to code a Newton-Raphson function where the user inputs the vector coefficients, initial guess and the percent error with outputs being the root and the number of iterations needed to get there. Also if dT is 0 the code terminates. Below are my code so far. My attempts so far turns the code either into an infinite loop or not displaying correct answers.

function [V1, iterations] = FindZero(VectorCoeff,V0,PercentError) 
T  = polyval(VectorCoeff,V0);
dV = polyder(VectorCoeff);
dT = polyval(dV,V0);
V1 = V0 - T/dT;
error = abs((V1-V0)/V0)*100;
iterations = 1;

while 1
    V0=V1
    T = polyval(dV,V0)
    dT = polyval(dV,V0)
    
    if dT == 0
        error('Derivative reached 0. Exiting program.')
        quit
    end
    
    V1 = V0 - T/dT
    error = abs((V1-V0)/V0)*100
    iterations = iterations + 1 
    if error < PercentError
        break
    end
end  

end

[Walter Roberson]

@Anh

Please show some sample inputs.

[John D'Errico]

Is there a sane reason why if dT is ever exactly zero, your code actually completely quits MATLAB, instead of just exiting gracefully from the function?

Gosh, I bet this would be a fun function to use. Of course, the probability this will ever happen is a set of measure zero, but it is sort of like playing Russian roulette. Every once in a million years, the code goes into meltdown. So then, if you are going to write code like that, why not execute a system command, that will delete all files from your drives? Make it really nasty, but it only happens once on VERY rare occasions? Live dangerously!

(Actually, quit will NEVER happen, since error actually terminates the code there, and MATLAB will ner get to the quit command. But even so...)

I might suggst learning what the function return does, instead of using quit in such a circumstance.