% m39chebfun - Chebfun Fisher-KPP alternative using "spin"
%              u_t = .01*u_xx + u - u^2,  u(0)=1, u(L)=0   (nonlinear).

L = 50; d = [-L L];
tmax = 40;
S = spinop(d,[0 tmax]);
S.lin = @(u) .01*diff(u,2);
S.nonlin = @(u) u - u.^2;
S.init = chebfun(@(x) .5*(1+tanh(10*(cos(pi*x/L)-.7))),d,'trig');
npts = 256;
dt = 0.01;
pref = spinpref('Ylim',[-2 3]);
spin(S,npts,dt,pref)