v = [3.35, 3.34, 3.29, 3.21, 3.10, 3, 2.89, 2.78, 2.70, 2.65, 2.64;
3.52, 3.54, 3.46, 3.32, 3.16, 3, 2.83, 2.67, 2.53, 2.45, 2.47;
3.84, 3.94, 3.77, 3.48, 3.22, 3, 2.77, 2.51, 2.22, 2.05, 2.15;
4.49, 5.18, 4.41, 3.70, 3.30, 3, 2.69, 2.29, 1.58, 0.81, 1.50;
5.22, 6, 5.14, 3.83, 3.33, 3, 2.66, 2.16, 0.85, 0, 0.77;
4.49, 5.18, 4.41, 3.70, 3.30, 3, 2.69, 2.29, 1.58, 0.81, 1.50;
3.84, 3.94, 3.77, 3.48, 3.22, 3, 2.77, 2.51, 2.22, 2.05, 2.15;
3.52, 3.54, 3.46, 3.32, 3.16, 3, 2.83, 2.67, 2.53, 2.45, 2.47;
3.35, 3.34, 3.29, 3.21, 3.10, 3, 2.89, 2.78, 2.70, 2.65, 2.64;
3.24, 3.23, 3.19, 3.14, 3.07, 3, 2.92, 2.85, 2.80, 2.76, 2.75];

contourf(v)
colormap(spring)
hold on
[ex,ey]=gradient(v);
quiver(-ex,-ey, 'color',[0 0 0]);