Error in KPZ (line 13) surf(x,t,w)

Dear friends. I am trying this but there is a problem in all "s"

What should I do in order to dial with this situation?

opts = odeset('RelTol',1e-8,'AbsTol',1e-8);

N=200; xi=0.02; xf=0.5; ti=1; tf=100; TIME=tf-ti;

%x=1:0.5:15;

%t=1:100:28800;

x = linspace(xi,xf,N);

t = linspace(ti,tf,200);

m = 0;

tic

sol = pdepe(m,@heat1D,@heatIC,@bcfun,x,t);

toc

w = sol(:,:,1);

surf(x,t,w)

xlabel('x')

ylabel('t')

zlabel('w(x,t)')

view([40 55])

%plot(w(200,:))

function [c,f,s] = heat1D(x,t,w,dwdx)

D=0.5; %0.2;

c = 1;

f = 1/2.*D*dwdx;

s = 100*dwdx.^2; %% NO NOISE

%s = 0.5*dwdx.^2 + 0.5/t; %%White

%s = 0.5*dwdx.^2 - 1/(x*sqrt(t)); %%Pink

%s = 3*dwdx.^2 - 0.1/(x*x); %%Brown

%s = -55/2*dwdx.^2 - 0.1*exp(-x*x/t)/t; %%Gauss

end

function w0 = heatIC(x)

%w0 =2;

w0=0.1*sin(2*x)+0.1*cos(2*x);

%w0=-0.5-0.3/(x+0.1)^2;

end

function[pl,ql,pr,qr]=bcfun(xl,ul,xr,ur,t)

pl = ul;

ql = 0;

pr = 0;

qr = 1;

end