function [A,b] = ssnormal(rv,c)
% Construct normal equations for spectral disentangling problem.
% This routine works.
%
% by D. Holmgren, April 12 94. holmgren@phobos.astro.uwo.ca

% Input data...
nl = input(' Length of spectra: ');
mrv = input(' Number of spectra: ');
% set up arrays...
a11 = zeros(nl,nl);
a12 = a11;
a22 = a11;
c1 = zeros(nl,1);
c2 = zeros(nl,1);
% i1,i2 will point to start and end of spectra in
% vector c...
i1 = 1;
i2 = nl;
for i = 1:mrv
% get appropriate rv differences...  
  rva = rv(i,1);
  rvb = rv(i,2);
% get corresponding spectrum...
  ci = zeros(nl,1);
  ci = c(i1:i2);
% generate matrices Na, Nb...  
  na = ssmat2(nl,rva);
  nb = ssmat2(nl,rvb);
% add these onto normal equations...  
  a11 = a11 + na' * na;
  a22 = a22 + nb' * nb;
  a12 = a12 + na'* nb;
% and the RHS...  
  c1 = c1 + na' * ci;
  c2 = c2 + nb' * ci;
  i1 = i1 + nl;
  i2 = i2 + nl;
end
% construct normal equation matrix and RHS vector...
A = [a11, a12; a12, a22];
b = [c1; c2];