function dcdt = cdot_conc_full(t,conc,D,P,K,vol,x,x_mid);

% function dcdt = cdot_new_conc(t,conc,D,P,K,vol,x,x_mid);
% new cdot file in concentration form
% for full equation

[M,N] = size(conc);

dx = diff(x);                               % face to face distance, (n-1) 
dx_mid = diff(x_mid);                       % center to center distance, (n-2)

% augment for ghost cells to make no flux BCs
aug_conc = [conc(1) ; conc(:) ; conc(end)];          % cell quantity
dx_mid = [dx_mid(1) ; dx_mid(:) ; dx_mid(end)];      % face quantity

% now find cdot
flux_face = D.*(diff(aug_conc)./dx_mid);             % face quantity
dcdt = 1./vol.*diff(flux_face)./dx - K.*conc + P;     % back to cell quantity  
