MATLAB: “Input arguments for contour must be real.

I have an error in contourf function : "Input arguments for contour must be real. Use the function REAL to get the real part of the inputs."

I've checked the input file ,the data are all real numbers. Here's the code.

Thanks for your help .

[X, Y]=meshgrid(-5:0.1:5);

Z=cos(X).*cos(X).*log(Y);

C=contourf(X,Y,Z);

clabel(C)

grid on

figure

plot3(X,Y,Z);

hold on

grid on

xlabel('x');

ylabel('y');

title('Лінії рівня');

[res1,Fmin1]=fminsearch('f2',[-3.1,0.001])

plot3(res1(1),res1(2),Fmin1,'ro-');

[res2,Fmin2]=fminsearch('f2',[0.1,0.001])

plot3(res2(1),res2(2),Fmin2,'ro-');

[res3,Fmin3]=fminsearch('f2',[3.1,0.001])

plot3(res3(1),res3(2),Fmin3,'ro-');

figure

C=contourf(X,Y,Z);

clabel(C)

grid on

hold on

plot(res1(1),res1(2),'ro-');

plot(res2(1),res2(2),'ro-');

plot(res3(1),res3(2),'ro-');