Spatial discretization has failed. Discretization supports only parabolic and elliptic equations, with flux term involving spatial derivative.

Hello,

Could you guys tell me what's wrong with the code. I'm trying to solve a Becker-Doring equation with diffusion. I am allowing only 4 clusters u1, u2, u3, u4 and the number of particles to be 9 which makes my Initial condition. Here is the code:

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function [c,b,s] = eqn2(x,t,u,DuDx)

c = [1; 1; 1; 1]; b = [1; 1; 1; 1].*DuDx; s=[ -u(1)*u(1) -u(1)*u(2) -u(1)*u(3) - u(1)*u(4) + 2*(10^-6)*u(2) + (10^-6)*u(3) +(10^-6)*u(4); -u(1)*u(2) + (u(1)^2)/2 +(10^-6)*u(3); -u(1)*u(3) +u(1)*u(2) - (10^-6)*u(3) + (10^-6)*u(4);u(1)*u(3) - (10^-6)*u(4)];

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function value = initial2(x) %INITIAL2: MATLAB function M-file that defines initial conditions %for a system of two PDE in time and one space variable. value = [9; 0; 0; 0]; _________________________________________________

function [pl,ql,pr,qr] = bc2(xl,ul,xr,ur,t) %BC2: MATLAB function M-file that defines boundary conditions %for a system of two PDE in time and one space dimension. pl = [0; ul(2);ul(3);0]; ql = [1; 0;0;1]; pr = [ur(1)-1; 0;0;0]; qr = [0; 1;0;1];

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m = 0; x = linspace(0,1,100); t = linspace(0,1,100); sol = pdepe(m,@eqn2,@initial2,@bc2,x,t); u1 = sol(:,:,1); u2 = sol(:,:,2); u3 = sol(:,:,3); u4 = sol(:,:,4); subplot(2,1,1) surf(x,t,u1); subplot(2,1,2) surf(x,t,u2);