Spacial discretization has failed

function mod_sim
global k Da v ua0 ual;
k = 200;
Da = 10^-9;
v = 1;
ua0 = 2453;
ual = 300;

tend =10;
m=0;
L = 1;
x = linspace(0,L,200);
t = linspace(0,tend,50);

sol = pdepe(m,@pdex1pde,@pdex1ic,@pdex1bc,x,t);

end

function [c,f,s] = pdex1pde(x,t,u,DuDx)
global k Da v
c=1;
f = Da*DuDx;
s =-k*u;

end

function u0 = pdex1ic(x)
 u0 =0;
end

function [pl,ql,pr,qr] = pdex1bc(xl,ul,xr,ur,t)
global ua0 ual;
pl=ul-ua0;
ql = 0;
pr = ur -ual;
qr=0;

end

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

derivative.I don't know why this error is showing .Can anybody help me why and how to rectify it.

[Torsten]

Start with k = 0 , ua0 = 1 and ual = 0 and slowly make changes in the settings towards your real problem.