function vfine=ctof(vcoarse)
% CTOF coarse to fine intergrid transfer by interpolation
%
% function vfine=ctof(vcoarse)
%
nc=length(vcoarse); %nc = 2^lc +1
nf=2*(nc-1)+1;
vfine=zeros(nf,1);
vfine(1:2:nf)=vcoarse;
vfine(2:2:nf-1)=.5*(vfine(1:2:nf-2)+vfine(3:2:nf));