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1 function [deltas, idx, weights] = get_fo_deltas(r, X, rectify)
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2 % [deltas, idx, (weights)] = get_fo_deltas(r, X)
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3 %
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4 % returns the difference vectors (dist(a,c) > dist(a,b))
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5 % for a given ranking:
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6 % deltas{i}(:,1) = a - b, deltas{i}(:,2) = a - c;
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7 %
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8 % set rectify to output absolute values of training examples
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9
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10 if nargin < 3
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11 rectify = 0;
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12 end
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13
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14 % ---
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15 % NOTE: this preallocation is not complete
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16 % ---
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17 deltas = {};
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18 idx = {};
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19 weights = [];
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20 for i = 1:size(r,1)
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21
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22 % feature index
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23 a = i;
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24
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25 % check if ranking is valid
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26 if ~isempty(r{i,1}) && ~isempty(r{i,2})&& ...
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27 isempty(intersect(r{i,1}, r{i,2}));
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28
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29 % ---
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30 % NOTE / TODO: the follwing is intended for compability
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31 % both sides of the ranking may have more than one entry.
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32 % for the MTT database, the ranking may be correct, but the
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33 % inequalities build from non-singular rankings are not
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34 % based on the actual data
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35 % ---
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36 for j = 1:numel(r{i,1})
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37 b = r{i,1}(j);
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38
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39 for k = 1:numel(r{i,2})
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40 c = r{i,2}(k);
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41
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42 % ---
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43 % get vector deltas,
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44 % NOTE: first: dissimilar, then similar pair
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45 % ---
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46 [dac] = X(:,a) - X(:,c);
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47 [dab] = X(:,a) - X(:,b);
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48
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49 if ~rectify
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50 deltas{end+1} = [dac dab];
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51 else
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52 % ---
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53 % rectify the data for training
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54 % ---
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55 deltas{end+1} = abs([dac dab]);
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56 end
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57
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58 idx{end+1} = {[a c],[a b]};
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59
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60 % save weights
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61 if size(r,2) == 3
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62 weights(end+1) = r{i,3}(1);
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63 end
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64 end
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65 end
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66 end
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67 end
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68 end
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69
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