how solve this problem in code execution

i have error in the following program

function dMt = fcn(dB,B,H, M, dH)

if dB~=0;

deltaB =1

k1=0.011;

k2=0.49;

mui0=4*pi*10e-07;

psi=30;

Ms=1.22e06;

alpha=5e-4;

L=3;

a=200;

c=0.6;

syms theta E1 E2 Ms theta

% theta=30;

Kan=4.03e4;

He=H+alpha*M;

p=k1*dB+deltaB*k2*abs(sqrt(dB));

E1=(He/a)*cos(theta)-(Kan/Ms*mui0*a)*sin(psi-theta)*sin(psi-theta);

E2=(He/a)*cos(theta)-(Kan/Ms*mui0*a)*sin(psi+theta)*sin(psi+theta);

% E1 = sym('E1');

% E2 = sym('E2');

% Ms = sym('Ms');

f1 = sin(theta)*cos(theta)*exp(E1 + E2);

f2 = sin(theta)*exp(E1 + E2);

Man = Ms * int(f1, 0, pi) / int(f2, 0, pi);

dMan=(Ms/a)*(1-coth(He/a)*coth(He/a)+(a/He)^2);

Mirr=(M-c*Man)/(1-c);

if((Man-Mirr)*dB)<0

dM=((c/mui0)*dMan)/(1-c*(alpha-1)*dMan);

else dM=(M-Man-(k*deltaB*c/(1-c))*(dMan)+p)/(mui0*(alpha-1)*(Man-M+(k*deltaB*c/(1-c))*(dMan)-(mui0*k*deltaB/(1-c))));

end

end

dMt =dM*dB;

Conversion to logical from sym is not possible.

Error in fcn (line 29)

if((Man-Mirr)*dB)<0

any one can help

Answer 1

[Luca Ferro]

you declared Ms on line 8 as:

Ms=1.22e06;

but then on line on line 13 you syms it

syms theta E1 E2 Ms theta

so this 3 assignments are considering Ms as syms, not 1.22e06

Man = Ms * int(f1, 0, pi) / int(f2, 0, pi);

dMan=(Ms/a)*(1-coth(He/a)*coth(He/a)+(a/He)^2);

Mirr=(M-c*Man)/(1-c);

since both Man and Mirr depend on the never solved syms Ms, this conditional expression cannot be evaluated

if((Man-Mirr)*dB)<0

Just decide which definition of Ms you want, and if you choose to keep the syms, solve it before using it in the conditional statement.