function [qn,q] = importanceweights(xu,y,R,q1);% PURPOSE : Computes the normalised importance ratios for the %           model described in the file sirdemo1.m.% INPUTS  : - xu = The predicted state samples.%           - y = The output measurements.%           - R = The measurement noise covariance.% OUTPUTS : - q = The normalised importance ratios.% AUTHOR  : Nando de Freitas - Thanks for the acknowledgement :-)% DATE    : 08-09-98if nargin < 3, error('Not enough input arguments.'); end[rows,cols] = size(xu);q = zeros(size(xu));qn = zeros(size(xu));m = (xu.^(2))./20;for s=1:rows,  q(s,1) = q1(s,1).*exp(-.5*R^(-1)*(y- m(s,1))^(2));end;a=sum(q(:,1));for s=1:rows,    qn(s,1)=q(s,1)./a;end;subplot(224); plot(xu,q,'+')      ylabel('Likelihood function','fontsize',15);xlabel('Hidden state support','fontsize',15)axis([-30 30 0 0.03]);