error in fourie script

hi I use MatLab 2016a and write this script but I receive this error. how should I fix it:

g=@(x)1.*(x>0)+(-1).*(x<0)
a_0=(1/pi)*quad(g,-pi,pi);
for n=1:10
    a_n(n)=(1/pi)*quad(g*cos(n*x),-pi,pi);
    b_n(n)=(1/pi)*quad(g*sin(n*x),-pi,pi);
end
a_n
b_n
f=a_0;
for n=1:10
    f=f+a_n(n)*cos(n*x)+b_n(n)*sin(n*x);
end
ezplot(x,f)

Answer 1

[VBBV]

g=@(x) 1.*(x>0)+(-1).*(x<0);

a_0=(1/pi)*quad(g,-pi,pi)

a_0 = 0

x = linspace(-pi,pi,200);    
for k = 1:numel(x)
    for n=1:10
        a_n(n,k)=(1/pi)*(g(x(k))*cos(n*x(k))); 
        b_n(n,k)=(1/pi)*(g(x(k))*sin(n*x(k))); 
        
    end
    A_n(k) = sum(a_n(:,k));
    B_n(k) = sum(b_n(:,k));
    f(k)=a_0+A_n(k).*cos(n.*x(k))+B_n(k).*sin(n.*x(k));
end 

plot(x,f)