matlab中Index exceeds matrix dimensions.错误

matlab中Index exceeds matrix dimensions.错误
function [x,m]=g1(x)
syms z k m x h
z(1)=30;
z(2)=68;
z(3)=75;
z(4)=82;
z(5)=82;
z(6)=77;
z(7)=68;
z(8)=68;
z(9)=58;
z(10)=51;
z(11)=50;
z(12)=41;
z(13)=38;
z(14)=35;
z(15)=28;
z(16)=25;
z(17)=18;
z(18)=15;
z(19)=12;
z(20)=10;
z(21)=7;
z(22)=7;
z(23)=4;
m=0;
h=0.25;
for k=4:x(2)
m=m+z(k-1)-z(k)-x(1)*h/24*(9*z(k)+19*z(k-1)-5*z(k-2)+z(k-3));
end
function [x,m]=gg(x)
syms m h1 h2 h3 i d y x
m=0;
d=2*0.13;
h1=0.25;
h2=0.5;
h3=1;
for i=5:5
y=[x(1),i];
m=m+(d*((1-x(2)*h1)^(i-1)-(1-x(2)*h1)^2)-g1(y))^2;
end
for i=6:12
y=[x(1),i];
m=m+(d*((1-x(2)*h2)^(i-1)-(1-x(2)*h2)^2)-g2(y))^2;
end
for i=13:23
y=[x(1),i];
m=m+(d*((1-x(2)*h3)^(i-1)-(1-x(2)*h3)^2)-g3(y))^2;
end
syms x0 x
x0=[0,0];
x=fminunc(gg,x0)
结果运行显示Index exceeds matrix dimensions.怎么回事?