clear
n = 20;
x = linspace(0,1,n);
u(1:n,1) = sin(pi*x);
h=x(2)-x(1);
dt = 0.45*h^2;
for j=1:100
u(1,j)=0;
u(n,j)=0;
end
for j=1:100
for i=2:n-1
u(i,j+1) = u(i,j)+dt/h^2*(u(i+1,j)-2*u(i,j)+u(i-1,j));
end
plot(x,u(1:n,j),'ko-')
hold on
end