Error using surf (line 75) Data dimensions must agree. Error in wode (line 64)

% 绘制目标函数曲线图
xx1=0:50:600;
xx2=130:5:150;
for i=1:length(xx1)
    for j=1:length(xx2)
        if(4.6084*xx1(i)^5-xx2(j)<=0 )
            Z(i,j)=xx1(i)^2+xx2(j)^2;
        else
            Z(i,j)=0;
        end
    end
end
figure(1);
surf(xx1,xx2,Z);
axis([0 600 130 150 0 10000])
title('目标函数曲线图');
xlabel('x1');
ylabel('x2');
运行后总是出现这种问题怎么办？