rafisher2cda.m

Fisher线性判别分类器应用于IRIS数据集的例子

function [RAFisher2cda] = RAFisher2cda(X,pp,c,alpha)
% RAFISHER2CDA Canonical Discriminant Analysis.
%
%[As well as the previous RAFisher1, this file was named RAFisher2 in honor to 
%Sir Ronald Aylmer Fisher (17 Feb.,1890-29 Jul.,1962), one of the most insightful
%and influential statisticians of all times. His pioneering work on discriminant 
%functions was made in 1936 (a pdf file of this paper is attached in this zip), 
%presenting an analysis on data collected by Edgar Anderson on three species of
%iris flowers (a classical set of multivariate data and also attached in this zip).]
%
%-Again, we encourage to all the users to initiate a chain of petitions to make 
%possible to carry to the big or small screen the life of this notable genius of our
%time. A possible title of the film would be 'Fisher's geometric mind'.-His work shaped
%the world of statistics, he made it as we know it today.-
%
%While RAFisher1 is a procedure that produces very different functions for classification
%that are also called linear discriminant analysis, RAFisher2cda is a dimension-reduction
%technique related to principal component analysis and canonical correlation called 
%canonical discriminant analysis. It derives the canonical coefficients parallels that
%of one-way MANOVA and it finds linear combinations of the quantitative variables that
%provide maximal separation between the classes or groups in much the same way that 
%principal components summarize total variation. The output produced are the canonical
%coefficients and the scored canonical variables. The canonical coefficients are rotated.
%Also, it proceeds with a Bartlett's approximate chi-squared statistic for testing the 
%canonical correlation coefficients.
%
%In summary, the canonical discriminant analysis:

%      - Transform the variables so that the pooled within-group covariance matrix is
%        an identity matrix.
%      - Compute group means on the transformed variables.
%      - Perform a principal component analysis on the means, weighting each mean by
%        the number of observations in the group. The eigenvalues are equal to the ratio
%        of between-group variation to the within-group variation in the direction of
%        each principal component. Here, the principal component analysis is runned by
%        the singular value decomposition.
%      - Back-transform the principal components into the space of the original variables,
%        obtaining the canonical variables.
%
%File gives you the option to get an unbiased or maximum-likelihood parameter estimation.
%
%   Syntax: function [RAFisher2cda] = RAFisher2cda(X,pp,c,alpha) 
%      
%     Inputs:
%          X - multivariate data matrix. 
%         pp - vector of prior probabilities (unknown,pp = 1;
%              known [default], pp = 2 [you must to give it]).
%          c - asking for ellipse confidence bounds (yes:c = 1;
%              [default], no:c = 2).
%      alpha - significance level (default = 0.05). Used for the 
%              Chi-square tests and for the ellipse confidence bounds.
%      
%     Output:
%          - Canonical discriminant functions. It includes:
%            constant, variates, eigenvalues, percentages and
%            cumulative percentages. Also the Bartlett's approximate 
%            chi-squared statistic for testing the canonical correlation
%            coefficients. Optionally, it also can show you the pair-wise
%            canonical scores with its ellipses confidence bounds.
%
%    Example: From the Table 11.5 (Iris data) of Johnson and Wichern (1992, p. 562), 
%             with 150 observations (n = 150), four variables (p = 4) [all = cm] and 
%             three groups (g = 3; sizes: 50,50,50). We are interested to apply a 
%             Canonical Discriminant Analysis with an unbiased parameter estimation.
%             It is considering equal prior probabilities (pp = 1) and the groups
%             ellipse bound with a probability of 0.95 (alpha value of 0.05).
%
%        ------------------------------------------------------------------------------
%                   1                          2                          3 
%        ------------------------------------------------------------------------------
%          x1    x2    x3    x4       x1    x2    x3    x4       x1    x2    x3    x4  
%        ------------------------------------------------------------------------------
%         5.1   3.5   1.4   0.2      7.0   3.2   4.7   1.4      6.3   3.3   6.0   2.5
%         4.9   3.0   1.4   0.2      6.4   3.2   4.5   1.5      5.8   2.7   5.1   1.9
%         4.7   3.2   1.3   0.2      6.9   3.1   4.9   1.5      7.1   3.0   5.9   2.1
%         4.6   3.1   1.5   0.2      5.5   2.3   4.0   1.3      6.3   2.9   5.6   1.8
%         5.0   3.6   1.4   0.2      6.5   2.8   4.6   1.5      6.5   3.0   5.8   2.2
%         5.4   3.9   1.7   0.4      5.7   2.8   4.5   1.3      7.6   3.0   6.6   2.1
%          .     .     .     .        .     .     .     .        .     .     .     .
%          .     .     .     .        .     .     .     .        .     .     .     .
%          .     .     .     .        .     .     .     .        .     .     .     .
%         5.1   3.8   1.6   0.2      5.7   2.9   4.2   1.3      6.3   2.5   5.0   1.9
%         4.6   3.2   1.4   0.2      6.2   2.9   4.3   1.3      6.5   3.0   5.2   2.0
%         5.3   3.7   1.5   0.2      5.1   2.5   3.0   1.1      6.2   3.4   5.4   2.3
%         5.0   3.3   1.4   0.2      5.7   2.8   4.1   1.3      5.9   3.0   5.1   1.8
%        ------------------------------------------------------------------------------
%
%      Group 1 = Iris setosa (n1 = 50); Group 2 = Iris versicolor (n2 = 50);
%      Group 3 = Iris virginica (n3 = 50).
%      Var1 (x1) = sepal length; Var2 (x2) = sepal with;
%      Var3 (x3) = petal length; Var4 (x4) = petal with.
%
%             Total data matrix must be:
%      You can get the X-matrix by calling to iris data file provided in
%      the zip as 
%                    load path-drive:irisdata 
% 
%             Calling on Matlab the function: 
%                RAFisher2cda(X,1)
%
%             Answer is:
%
%  It was asking for the ellipses confidence bounds. 
%  Do you want an unbiased (1) or maximum-likelihood parameter estimation? (2):1
% 
%  Canonical Discriminant Functions.
%  --------------------------------------------------------------------------------
%  Constant =
%     -2.1051    6.6615
%
%  Variates =
%      0.8294    0.0241
%      1.5345    2.1645
%     -2.2012   -0.9319
%     -2.8105    2.8392
%
%  Eigenvalue =
%     32.1919    0.2854
%
%  Percentage =
%     99.1213    0.8787
%
%  CumulativePercentage =
%     99.1213  100.0000
%  --------------------------------------------------------------------------------
%  Functions = columns. On variates, Variate1 = first row and so forth to 4
%
%  Chi-square Tests with Successive Roots Removed.
%  -------------------------------------------------------------------------
%  Removed    Eigenvalue   CanCor      LW       Chi-sqr.     df       P
%  -------------------------------------------------------------------------
%              32.1919     0.9848    0.0234     546.1153      8    0.0000
%     1         0.2854     0.4712    0.7780      36.7807      3    0.0000
%  -------------------------------------------------------------------------
%  With a given significance of: 0.05
%  If P-value >= alpha, results not significative. Else, it is significative.
%
%  The pair-wise plots you can get are: 1
%  --------------
%  plots =
%
%       1     2
%
%  --------------
%  Give me the pair of factors to plot [a b]: [1 2]
%  Do you need another plot? (y/n): n
%
%
%  Created by A. Trujillo-Ortiz, R. Hernandez-Walls and S. Perez-Osuna
%             Facultad de Ciencias Marinas
%             Universidad Autonoma de Baja California
%             Apdo. Postal 453
%             Ensenada, Baja California
%             Mexico.
%             [e-mail]
%
%  Copyright (C)  April 15, 2004. 
%
%  To cite this file, this would be an appropriate format:
%  Trujillo-Ortiz, A., R. Hernandez-Walls and S. Perez-Osuna. (2004). 
%    RAFisher2cda:Canonical Discriminant Analysis. A MATLAB file. 
%    [WWW document]. URL http://www.mathworks.com/matlabcentral/fileexchange/
%    loadFile.do?objectId=4836&objectType=FILE
%
%  References:
% 
%  Johnson, R. A. and Wichern, D. W. (1992), Applied Multivariate Statistical Analysis.
%              3rd. ed. New-Jersey:Prentice Hall. Chapter 11, pp. 493-572.
%  Fisher, R. A. (1936), The use of multiple measurements in taxonomic problems. Annals
%              of Eugenics, 7: 179-188.
%

if nargin < 4,
   alpha = 0.05; %(default)
end; 

if (alpha <= 0 | alpha >= 1)
   fprintf('Warning: significance level must be between 0 and 1\n');
   return;
end;

if nargin < 3, 
   c = 1; %(default)
end;

disp(' ')
if c == 1;
   fprintf('It was asking for the ellipses confidence bounds.');
else c == 2;
   fprintf('It was not asking for the ellipses confidence bounds.');
end;
disp(' ')

if nargin < 2,
   pp = 1; %(default)
end;

if nargin < 1, 
   error('Requires at least one input arguments.');
   return;
end;

Y = X(:,2:end);
G = X(:,1);

g = max(G);  %number of groups

%Vector of sample sizes per group.
n = [];
indice = X(:,1);
for i = 1:g
   Xe = find(indice==i);
   eval(['X' num2str(i) '= X(Xe,2);']);
   eval(['n' num2str(i) '= length(X' num2str(i) ') ;'])
   eval(['xn = n' num2str(i) ';'])
   n = [n,xn];
end;

r = 1;
r1 = n(1);

%Partition of the group mean and covariance matrices.
M = [];
for k = 1:g
   eval(['M' num2str(k) '= mean(Y(r:r1,:));']);
   eval(['m = M' num2str(k) ';'])
   if k < g
      r = r+n(k);
      r1 = r1+n(k+1);
   end;
   M = [M;m];
end;