MATLAB: To plot a introduced function

concurrenceplot3

hi. i wrote 4 functions. now i want to plot the forth function but it gives me errors. plz help me to plot it.
plot3(C(J,d),J,d)
function ha = H(J,d)
    sx=[0 1;1 0];
    sy=[0 -1i;1i 0];
    sz=[1 0;0 -1];
    ha = J/2*(kron(sx,sx)+kron(sy,sy)+kron(sz,sz))+d*(kron(sx,sy)-kron(sy,sx)); 
end
function ro = R(J,d)
    T=0.5;
    ro = expm(-H(J,d)/T)/trace(expm(-H(J,d)/T));
end
function la = landa(J,d)
    sy=[0 -1i;01i 0];
    s=kron(sy,sy);
    la = real(sqrt(eig(R(J,d)*s*conj(R(J,d))*s)));
end
function co = C(J,d)
    co=max(0,2*max(landa(J,d))-sum(landa(J,d)));
end

Best Answer

J=-1:.1:1;
d=0:.1:5;
[J,d]=meshgrid(J,d);
Z=zeros(size(J));
for i=1:size(J,1)
    for j=1:size(J,2)
        Z(i,j)=C(J(i,j),d(i,j));
    end
end
surf(J,d,Z);
The above plots the surf plot of the J,d grid with height Z.
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