function outIndex = residualR(inIndex,q);
% PURPOSE : Performs the resampling stage of the SIR
% in order(number of samples) steps. It uses Liu's
% residual resampling algorithm and Niclas' magic line.
% 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.
% RESIDUAL RESAMPLING:
% ====================
N_babies= zeros(1,S);
% first integer part
q_res = S.*q'; %'
N_babies = fix(q_res);
% residual number of particles to sample
N_res=S-sum(N_babies);
if (N_res~=0)
q_res=(q_res-N_babies)/N_res;
cumDist= cumsum(q_res);
% generate N_res ordered random variables uniformly distributed in [0,1]
u = fliplr(cumprod(rand(1,N_res).^(1./(N_res:-1:1))));
j=1;
for i=1:N_res
while (u(1,i)>cumDist(1,j))
j=j+1;
end
N_babies(1,j)=N_babies(1,j)+1;
end;
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
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