新手求助

拟合函数的代码如下：
clc,clear
data=[17,2.97;18,2.91;19,2.85;20,2.80;21,2.76;22,2.72;23,2.69;24,2.65;25,2.62;26,2.60;27,2.57;28,2.55;29,2.53;30,2.52;35,2.45;40,2.40;45,2.35;50,2.32;60,2.28;70,2.24;80,2.22;90,2.20;100,2.18;150,2.14;200,2.12];
init_lambda=[0,0];
lambda=fminsearch('fun_e3',init_lambda,[],data);
x=data(:,1);
y=data(:,2);
A=[exp(lambda(1)*x) exp(lambda(2)*x)];
a=A\y;
estimated_y=a(1)*exp(lambda(1)*x)+a(2)*exp(lambda(2)*x)
subplot(2,2,1);plot(x,y);
subplot(2,2,3);plot(x,y,'ro',x,estimated_y,'b-')
lambda(1)
lambda(2)
a(1)
a(2)
一直报错，
??? Attempt to execute SCRIPT fun_e3 as a function.
Error in ==> fminsearch at 175
fv(:,1) = funfcn(x,varargin{:});
求解