symmetricuncertainty.m

信息论的工具箱,比较稀有,希望对大家有用!

%SYMMETRICUNCERTAINTY symmetric redundancy measure for categorical-discrete 
%data
%   SU = SYMMETRICUNCERTAINTY(X,Y) returns the symmetric uncertainty between
%   the two column vectors X and Y containing categorical measures.
%
%   SYMMETRICUNCERTAINTY [1] computes a symmetric scaled information 
%   measure based on mutual information [2][3] normalized to entropies of 
%   each variable X and Y
%
%   Joaquin Goñi <[e-mail]> & 
%   Iñigo Martincorena <[e-mail]>
%   University of Navarra - Dpt. of Physics and Applied Mathematics &
%   Centre for Applied Medical Research. Pamplona (Spain).
%
%   December 13th, 2007. Information Theory Toolbox v1.0
%
%   Example:
%   
%       x = [1;2;2;2;0;0;1;0;1;2];
%       y = [1;2;2;2;2;1;0;2;1;0];
%       su = symmetricuncertainty(x,y);
%
%   Citation:
%
%   If you use them for your academic research work,please kindly cite this 
%   toolbox as: 
%   Joaquin Goñi, Iñigo Martincorena. Information Theory Toolbox v1.0.  
%   University of Navarra - Dpt. of Physics and Applied Mathematics & 
%   Centre for Applied Medical Research. Pamplona (Spain).
%
%   References
%   [1] Witten, Ian H. & Frank, Eibe (2005), Data Mining: Practical Machine 
%   Learning Tools and Techniques, Morgan Kaufmann, Amsterdam.
%   [2] C. E. Shannon, A mathematical theory of communication, Bell System 
%   Technical Journal, vol. 27, pp. 379-423 and 623-656, July and October, 
%   1948.
%   [3] http://en.wikipedia.org/wiki/Mutual_information

function su = symmetricuncertainty(x,y)

su = 2*redundancy(x,y); %SU = 2* I(X;Y) / (H(X) + H(Y)) = 2*R see redundancy for more information.