function[ffdb2] = compactdiffcabfdoctb2(VVb2,hb21);
% function to generate values of ffd using compact difference scheme
% calling sequence 
% [ffd] = compactdiffcabfdoct(V,hd1)
% define variables
% V1 -- function V1 generated at different points x1 by using function
% h21 -- h1*h1 ( where h is discretization interval ) h1 = 2/(n1-1)
% a -- coeff for boundaries
% b -- coeff for boundaries 
% c -- coefffor boundaries
% d -- coeff for boundaries
% e -- coeff for boundaries 
% alpha -- compact diff coeff
% alpha1 -- compact diff coeff
% A -- coeff forother points
% A1 -- coeff for other points 
% B -- coeff for other points 
% C -- coeff for other points
% f -- R.H.S of equation Ax = B
% N1 -- number of points of space discretization
% ii -- index variable 
% record of revisions 
% date                           Programmer                     Description of changes
% June 1, 2007                      Asha G                            original code
 % July 18, 08                     Asha G                          rewritten for first derivative 
  % March 8,08                      Asha G                         rewritten for cabranbact13oct
% June 5,13                         Asha G                         vectorised for loop  
% declare global values 
global N 
%pack ('compactdiffcabfdoctb2')

alphafd = 1/3;  %lele eqn 2.1.7
%alpha1 = 1/10;
alpha1fd = 1/4; % lele eqn 2.1.6
alphafdb = 2; % lele fig.6(e)
beta = 0;

% for boundaries % eqn 4.1.3
afd = -(11 + 2*alphafdb)/6; 
bfd = (6-alphafdb)/2;
cfd = (2*alphafdb -3)/2;
%dfd = (2-alphafdb)/6;
dfd = 0; % lele fig.6(e)

% for other points:
Afd = 14/9;
%A1 = (4/3)* (1-(alpha1));
A1fd = (2/3)*(alpha1fd + 2);
Bfd = 1/9;
C = 0;


ffdb2 = zeros(1,N);

%for ii = 3:(N-2)
%	 x = ((Bfd*(VVb2(ii+2)-VVb2(ii-2)))./(4*hb21))+ (Afd*(VVb2(ii+1)-VVb2(ii-1)))./(2*hb21);
%endfor 
%ffdb2 = x;
ii = 3:(N-2);
	  ffdb2(ii) = ((Bfd*(VVb2(ii+2)-VVb2(ii-2)))./(4*hb21)) + (Afd*(VVb2(ii+1)-VVb2(ii-1)))./(2*hb21);


ffdb2(1) = (afd*VVb2(1)+bfd*VVb2(2)+cfd*VVb2(3)+dfd*VVb2(4))./hb21;
ffdb2(N) = -(afd*VVb2(N)+ bfd*VVb2(N-1)+cfd*VVb2(N-2)+dfd*VVb2(N-3))./hb21;
ffdb2(2) =( A1fd*(VVb2(3)-VVb2(1)))./(2*hb21);
ffdb2(N-1)=(A1fd*(VVb2(N)-VVb2(N-2)))./(2*hb21);

endfunction % function compactdiffcabfdoctb2