Quad2d error: Improper index matrix reference.

Hello ,

I am trying to run a 2d integration but i keep getting the following error message:

Improper index matrix reference.

Error in @(phi,z)((M.*my0)/(2.*pi)).*((Z(k)-z).^2*((Z(k)-z).^2+R(k).^2-a.*R(k).*cos(phis-phi))-(((Z(k)-z).^2+R(k).^2).^(1/2)).*((a.^2+(Z(k)-z).^2+R(k).^2-2.*a.*R(k).*cos(phis-phi)).^(1/2)))./(((a.^2+(Z(k)-z).^2+R(k).^2-2.*a.*R(k).cos(phis-phi)).^(1/2)).*(2.*(Z(k)-z).^2+R(k).^2-R(k).^2.*cos(2.*(phis-phi))))

Error in integral2Calc>integral2t/tensor (line 229) Z = FUN(X,Y); NFE = NFE + 1;

Thank you for your help