??? Undefined function or method 'power' for input arguments of type 'function_handle'.

hello guys, I am quite new to matlab and am trying to do a newton-raphson iteration. but i keep getting this error: ??? Undefined function or method 'power' for input arguments of type 'function_handle'.

Error in ==> @(z)(z.^3-z.^2+m*z+m2)

Error in ==> graded_lab1 at 24 x1=y-(z1(z)/dz(z));

Some of the code i temporarily commented out. but i am also having trouble doing a for loop inside a for loop. Here's the code:

 %problem2
tc=373.56;
pc=88.9;
t=293;
p= [1 1.5 2 2.5 3 5 10 15 25 50];
r=8.3144621;
a=(r*r*(sqrt(tc*tc*tc*tc*tc)))/(9*pc*(sqrt(8)-1));
b=((sqrt(8)-1)*r*tc)/(3*pc);
A=(a*p)/(r*r*sqrt(t*t*t*t*t));
B=(b*p)/(r*t);
%for i=1:10
    m=(A(i)-B(i)-B(i)*B(i))
    m2=-A(i)*B(i)
    z1 = @(z) (z.^3-z.^2+m*z+m2);
    dz = @(z) 3*z.^2-2*z+m;
    y=0;
    for u=1:1:100
        x1=y-(z1(z)/dz(z));
        y=x1
        if x1==y break 
        end
    end
    %v(i)=(root(1)*r*t)/p(i);
%end
%v(3)=(Zed*r*t)/p
v
plot(v);

Answer 1

[Mischa Kim]

Suj, two things: root and Zed are not defined. In

x1 = y - (z1(z)/dz(z));

the running index is probably u, and not z, I assume.

[suj gal]

u is just for iterations from 1 to 100 no? i thought z1(z) would be referring to the function z?

[Mischa Kim]

OK. That's what you meant. I have started cleaning up your code. It's not quite done yet... but running.

 ...
 B = (b*p)/(r*t);

 del   = 1e-5;
 max_i = 10;
 v     = zeros(1,max_i);          % pre-allocate memory
 for ii = 1:max_i
    m  = (A(ii)-B(ii)-B(ii)*B(ii));
    m2 = -A(ii)*B(ii);
    z1 = @(z) (z.^3-z.^2+m*z+m2);
    dz = @(z) 3*z.^2-2*z+m;
    y  = 0;
    for u = 1:1:100
        deltaz = (z1(y)/dz(y));   % the arg seems to be y
        x1     = y - deltaz;
        if (abs(deltaz)< del)     % close enough to solution?
            v(ii) = x1;           % save solutions
            break 
        end
        y = x1;
    end
 end
 plot(v);