1 | function varargout = entropy(varargin) |
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2 | %ENTROPY |
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3 | % |
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4 | % y = ENTROPY(x) |
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5 | % |
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6 | % Computes/declares entropy -sum(x.*log(x)) |
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7 | % |
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8 | % Implemented as evalutation based nonlinear operator. Hence, the concavity |
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9 | % of this function is exploited to perform convexity analysis and rigorous |
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10 | % modelling. |
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11 | |
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12 | % Author Johan Löfberg |
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13 | % $Id: entropy.m,v 1.2 2006/08/16 09:06:57 joloef Exp $ |
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14 | |
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15 | switch class(varargin{1}) |
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16 | |
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17 | case 'double' % What is the numerical value of this argument (needed for displays etc) |
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18 | varargout{1} = -sum(varargin{1}.*log(varargin{1})); |
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19 | |
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20 | case 'sdpvar' % Overloaded operator for SDPVAR objects. |
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21 | if min(size(varargin{1}))>1 |
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22 | error('ENTROPY only defined for vector arguments'); |
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23 | else |
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24 | varargout{1} = yalmip('addEvalVariable',mfilename,varargin{1}); |
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25 | end |
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26 | |
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27 | case 'char' % YALMIP sends 'model' when it wants the epigraph or hypograph |
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28 | switch varargin{1} |
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29 | case 'graph' |
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30 | t = varargin{2}; |
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31 | X = varargin{3}; |
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32 | |
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33 | % This is different from so called extended operators |
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34 | % Just do it! |
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35 | F = SetupEvaluationVariable(varargin{:}); |
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36 | |
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37 | % Now add your own code, such as domain constraints |
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38 | F = F + set(X > 0); |
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39 | |
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40 | % Let YALMIP know about convexity etc |
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41 | varargout{1} = F; |
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42 | varargout{2} = struct('convexity','concave','monotonicity','increasing','definiteness','none'); |
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43 | varargout{3} = X; |
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44 | |
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45 | case 'milp' |
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46 | varargout{1} = []; |
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47 | varargout{2} = []; |
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48 | varargout{3} = []; |
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49 | otherwise |
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50 | error('SDPVAR/LOG called with CHAR argument?'); |
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51 | end |
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52 | otherwise |
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53 | error('SDPVAR/LOG called with CHAR argument?'); |
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54 | end |
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