xx=-3:.2:3;
tt=0.01:0.05:1;
k=0.2;
[X,T]=meshgrid(xx,tt);
F=(1./sqrt(4*pi*k.*T)).*exp(-X.^2./(4*k.*T));

figure(1)
surf(X,T,F)

figure(2)
mesh(F)

figure(3)
waterfall(F)

