Meshplot is not matching with the exact plot

I am using spectral methods on a heat equation to predict the results of a black-scholes equation but having trouble to match with the exact plot. The first plot is what is giving. but it was supposed to match with the second plot

function [D,x] = cheb(N)
%UNTITLED Summary of this function goes here
%   Detailed explanation goes here
if N==0,D=0;x=1;return,end 
x=cos(pi*(0:N)/N)'; 
c=[2;ones(N-1,1);2].*(-1).^(0:N)'; 
X=repmat(x,1,N+1); 
dX=X-X';
D=(c*(1./c)')./(dX+(eye(N+1))); 
D=D-diag(sum(D')); 
end
%Differentiatio matrix and initial data 
N=20; [D,x]=cheb(N);
D2=D^2; 
eps=1; 
dt=.01 
sigma=.10
r=.12; K=100; 
k=(2*r)/sigma^2; 
v=max(exp(((k+1)/2)*x)-exp(((k-1)/2)*x),0)
t=0;
l=0;
%Differentition matrix and initial data; 

%solve pde 
tmax=1,tplot=2
nplots=round(tmax/tplot)
plotgap=round(tplot/dt),dt=tplot/plotgap 
xx=0:.025:1; vv=polyval(polyfit(x,v,N),xx); 
plotdata=[vv;zeros(nplots,length(xx))]; tdata=t; 
for i=1:nplots
    for n=1:plotgap 
        t=t+dt,v=v+dt*(eps*D2*v),
        l=l+1
        v(1)=exp(((k-1)/2+((k+1)^2)/4)*t)*(exp(1)-exp(-k*t));
        v(end)=0; 
    end 
    vv=polyval(polyfit(x,v,N),xx); 
    plotdata(i+1,:)=vv;tdata=[tdata;t]; 
end 
clf,subplot('position',[.1 .4 .8 .5])
mesh(xx,tdata,plotdata),grid on 
axis([-1 1 0 tmax -1 2]), 
view(-60,55),colormap([0 0 0]),xlabel x,ylabel t,zlabel u