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function outIndex = multinomialR(inIndex,q); 
% PURPOSE : Performs the resampling stage of the SIR 
%           in order(number of samples) steps. 
% INPUTS  : - inIndex = Input particle indices. 
%           - q = Normalised importance ratios. 
% OUTPUTS : - outIndex = Resampled indices. 
% AUTHORS  : Arnaud Doucet and Nando de Freitas - Thanks for the acknowledgement. 
% DATE     : 08-09-98 
 
if nargin < 2, error('Not enough input arguments.'); end 
 
[S,arb] = size(q);  % S = Number of particles. 
 
% MULTINOMIAL SAMPLING: 
% ===================== 
N_babies= zeros(1,S); 
cumDist= cumsum(q');    
% generate S ordered random variables uniformly distributed in [0,1] 
% high speed Niclas Bergman Procedure 
u = fliplr(cumprod(rand(1,S).^(1./(S:-1:1)))); 
j=1; 
for i=1:S 
  while (u(1,i)>cumDist(1,j)) 
    j=j+1; 
  end 
  N_babies(1,j)=N_babies(1,j)+1; 
end; 
 
% COPY RESAMPLED TRAJECTORIES:   
% ============================ 
index=1; 
for i=1:S 
  if (N_babies(1,i)>0) 
    for j=index:index+N_babies(1,i)-1 
      outIndex(j) = inIndex(i); 
    end; 
  end;    
  index= index+N_babies(1,i);    
end