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1 function [bnet, Unode, Snode, Lnodes, Rnode, Ynode, Lsnode] = ...
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2 mk_gmux_robot_dbn(nlandmarks, Q, R, init_x, init_V, robot_block, landmark_block)
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3
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4 % Make DBN
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5
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6 % S
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7 % | L1 -------> L1'
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8 % | | L2 ----------> L2'
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9 % \ | /
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10 % v v v
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11 % Ls
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12 % |
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13 % v
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14 % Y
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15 % ^
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16 % |
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17 % R -------> R'
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18 % ^
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19 % |
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20 % U
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21 %
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22 %
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23 % S is a switch, Ls is a deterministic gmux, Y = Ls-R,
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24 % R(t+1) = R(t) + U(t+1), L(t+1) = L(t)
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25
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26
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27 % number nodes topologically
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28 Snode = 1;
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29 Lnodes = 2:nlandmarks+1;
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30 Lsnode = nlandmarks+2;
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31 Unode = nlandmarks+3;
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32 Rnode = nlandmarks+4;
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33 Ynode = nlandmarks+5;
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34
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35 nnodes = nlandmarks+5;
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36 intra = zeros(nnodes, nnodes);
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37 intra([Snode Lnodes], Lsnode) =1;
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38 intra(Unode,Rnode)=1;
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39 intra([Rnode Lsnode], Ynode)=1;
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40
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41 inter = zeros(nnodes, nnodes);
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42 inter(Rnode, Rnode)=1;
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43 for i=1:nlandmarks
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44 inter(Lnodes(i), Lnodes(i))=1;
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45 end
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46
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47 Lsz = 2; % (x y) posn of landmark
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48 Rsz = 2; % (x y) posn of robot
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49 Ysz = 2; % relative distance
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50 Usz = 2; % (dx dy) ctrl
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51 Ssz = nlandmarks; % can switch between any landmark
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52
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53 ns = zeros(1,nnodes);
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54 ns(Snode) = Ssz;
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55 ns(Lnodes) = Lsz;
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56 ns(Lsnode) = Lsz;
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57 ns(Ynode) = Ysz;
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58 ns(Rnode) = Rsz;
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59 ns(Ynode) = Usz;
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60 ns(Unode) = Usz;
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61
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62 bnet = mk_dbn(intra, inter, ns, 'discrete', Snode, 'observed', [Snode Ynode Unode]);
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63
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64
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65 bnet.CPD{Snode} = root_CPD(bnet, Snode); % always observed
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66 bnet.CPD{Unode} = root_CPD(bnet, Unode); % always observed
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67 for i=1:nlandmarks
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68 bi = landmark_block(:,i);
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69 bnet.CPD{Lnodes(i)} = gaussian_CPD(bnet, Lnodes(i), 'mean', init_x(bi), 'cov', init_V(bi,bi));
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70 end
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71 bi = robot_block;
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72 bnet.CPD{Rnode} = gaussian_CPD(bnet, Rnode, 'mean', init_x(bi), 'cov', init_V(bi,bi), 'weights', eye(2));
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73 bnet.CPD{Lsnode} = gmux_CPD(bnet, Lsnode, 'cov', repmat(zeros(Lsz,Lsz), [1 1 nlandmarks]), ...
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74 'weights', repmat(eye(Lsz,Lsz), [1 1 nlandmarks]));
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75 W = [eye(2) -eye(2)]; % Y = Ls - R, where Ls is the lower-numbered parent
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76 bnet.CPD{Ynode} = gaussian_CPD(bnet, Ynode, 'mean', zeros(Ysz,1), 'cov', R, 'weights', W);
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77
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78 % slice 2
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79 eclass = bnet.equiv_class;
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80 W = [eye(2) eye(2)]; % R(t) = R(t-1) + U(t), where R(t-1) is the lower-numbered parent
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81 bnet.CPD{eclass(Rnode,2)} = gaussian_CPD(bnet, Rnode+nnodes, 'mean', zeros(Rsz,1), 'cov', Q, 'weights', W);
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82 for i=1:nlandmarks
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83 bnet.CPD{eclass(Lnodes(i), 2)} = gaussian_CPD(bnet, Lnodes(i)+nnodes, 'mean', zeros(2,1), ...
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84 'cov', zeros(2,2), 'weights', eye(2));
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85 end
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