各位大神，本人小白，遇到一个棘手问题，查了好多资料还没解决，希望大神借力！
问题：
想拟合一个曲面并输出它的函数表达式。
开始用的sftool的多项式拟合，但只能拟合到5阶，结果不够精确，误差较大。
想编程拟合，又不知用哪个命令，求指点，能举个小李子最好，我可以模仿。
先谢过了！
p.s. 数据如下：
x=[-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.0609375,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.040625,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,-0.0203125,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.0203125,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.040625,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375,0.0609375];
y=[-0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625 -0.0609375 -0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625 0.05078125 -0.08125 -0.07109375 -0.0609375 -0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625 0.05078125 0.0609375 -0.086666666 -0.075833333 -0.065 -0.054166666 -0.043333333 -0.0325 -0.021666666 -0.010833333 0.010833333 0.021666666 0.0325 0.043333333 0.054166666 0.065 0.075833333 0.086666666 -0.08125 -0.07109375 -0.0609375 -0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625 0.05078125 0.0609375 -0.0609375 -0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625 0.05078125 -0.05078125 -0.040625 -0.03046875 -0.0203125 -0.01015626 0 0.01015625 0.0203125 0.03046875 0.040625];
z=[0.0163 0.0249 0.0265 0.0132 0.019 0.0334 0.0385 0.0999 0.1305 0.0283 0.003764 0.0166 0.0499 0.1525 0.313 0.319 0.3206 0.3332 0.3189 0.2782 0.2252 0.177 0.3434 0.3384 0.3219 0.3292 0.327 0.3335 0.351 0.3651 0.3417 0.3433 0.3303 0.3183 0.2965 0.236 0.0423 0.3767 0.3876 0.304 0.3434 0.3817 0.3716 0.3773 0.3797 0.3806 0.3763 0.3597 0.3392 0.1483 0.0163 0.0118 0.0118 0.3434 0.3384 0.3219 0.3292 0.327 0.3335 0.351 0.3651 0.3417 0.3433 0.3303 0.3183 0.2965 0.236 0.0423 0.003764 0.0166 0.0499 0.1525 0.313 0.319 0.3206 0.3332 0.3189 0.2782 0.2252 0.177 0.0163 0.0249 0.0265 0.0132 0.019 0.0334 0.0385 0.0999 0.1305 0.0283]