matlab 想画一个非线性的最小二次拟合，但执行部出来

clear;
x=[-2,-1.7,-1.4,-1.1,-0.8,-0.5,-0.2,0.1,0.4,0.7,1,1.3,1.6,1.9,2.2,2.5,2.8,3.1,3.4,3.7,4,4.3,4.6,4.9];
y=[0.1029,0.1174,0.1316,0.1448,0.1566,0.1662,0.1733,0.1775,0.1785,0.1764,0.1711,0.1630,0.1526,0.1402,0.1266,0.1122,0.0977,0.0835,0.0702,0.0588,0.0479,0.0373,0.0291,0.0224];
s0=[1,1];
s=lsqcurvefit('aa',s0,x,y);
f=aa(s,x);
plot(x,f);

function f=aa(s,x)
f=(1/(sprt(2pis(1)))exp((-(x-s(2))^2)/(2(s(1)^2)));
end

出错
出错 Untitled5 (line 5)
s=lsqcurvefit('aa',s0,x,y);

原因:
Failure in initial objective function evaluation. LSQCURVEFIT cannot
continue.

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