Asked by David Campbell
on 17 Jul 2013

Below is the code I am using, and the error message I recieve:

function y = firstorder(x)

mat = 'mnfepas';

props = material_data(mat);

S = props(1,3);

L = props(1,4);

J = props(1,5);

Tc = props(1,6);

Ns = props(1,8);

g = props(10);

T = 200;

B = 1;

muB = 9.27e-24; % units: Am^2 or J/T

kB = 1.3807e-23; % units: J/K

nu = 1.75;

y = (1/T)*(3*Tc*J*((0.5/J)*((2*J+1)*coth((J+0.5)*x/J)-coth(0.5*x/J)))/(J+1) + g*muB*J*B/kB + (9/5)*(((2*J+1)^4)-1)*Tc*nu*(((0.5/J)*((2*J+1)*coth((J+0.5)*x/J)-coth(0.5*x/J)))^3)/((2*J+2)^4))-x;

end

Then I use the following:

x0 = 3;

x = fzero(firstorder,x0);

And then I get the following error message:

Error using firstorder (line 21) Not enough input arguments.

Error in nonlinear_brillouin_solver (line 2) x = fzero(firstorder,x0);

the function y is discontinuous at zero due to the coth, and at some values of T the function will cross the x axis multiple times, so I should get multiple roots... i think

Any help would be greatly appreciated

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Answer by Matt J
on 17 Jul 2013

Accepted answer

Should be

x = fzero(@firstorder,x0);

David Campbell
on 17 Jul 2013

Answer by Youssef Khmou
on 17 Jul 2013

hi David,

if you have numerical values of the coefficients, you can use the function root instead as in this example :

**6 x^3 - 4 x^2 + 10 x + 6 =0**

R=roots([6 -4 10 6])

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