If I use the following function to obtain scatter matrices then how could I pass the input data to this function ,please help me if anybody know??

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Sayed Afreen 2017-7-6

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https://ww2.mathworks.cn/matlabcentral/answers/347618-if-i-use-the-following-function-to-obtain-scatter-matrices-then-how-could-i-pass-the-input-data-to-t

评论： Ameer Hamza 2018-11-6

function [B W]=scattermat(data,Y)
%FUNCTION THAT CALCULATES SCATTER MATRIX:
%   B:BETWEEN  CLASS SCATTER MATRIX
%   W:WITHIN CLASS SCATTER MATRIX
%
      [~, l]=size(data);         %CALCULATE SIZE OF DATA
      clases=unique(Y);          %GET VECTOR OF CLASSES
      tot_clases=length(clases); %HOW MANY CLASSES
      B=zeros(l,l);              %INIT B AND W
      W=zeros(l,l);           
      overallmean=mean(data);    %MEAN OVER ALL DATA
      for i=1:tot_clases
          clasei = find(Y==clases(i)); %GET DATA FOR EACH CLASS
          xi=data(clasei,:);
          mci=mean(xi);                       %MEAN PER CLASS
          xi=xi-repmat(mci,length(clasei),1); %Xi-MeanXi
          W=W+xi'*xi;                         %CALCULATE W
          B=B+length(clasei)*(mci-overallmean)'*(mci-overallmean); %CALCULATE B
      end
  end

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Sayed Afreen 2017-7-6

I am not using this code as it is ,I just want to clear my doubt which I have explain above.please dont mine but I already done with my own code ,I thought that if I ask the question on this code then may be my error will be removed because my code related somewhat to above code.Thanks!!

Jan 2017-7-6

@Sayed: Okay. I really like well documented code, which explains the inputs, actions and the output exhaustively with the obvious intention to make it as easy and trustworthy as possible to use the code. This does not help only other, but the author also after some month, when the exact intention of the code has been forgotton. Note that the code lines itself are well documented. Only the meaning of the inputs have been forgotten.

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Answer 1

Walter Roberson 2017-7-6

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https://ww2.mathworks.cn/matlabcentral/answers/347618-if-i-use-the-following-function-to-obtain-scatter-matrices-then-how-could-i-pass-the-input-data-to-t#answer_273151

The first input needs to be a 2D array with one sample per row. The second input needs to be a numeric vector of class numbers, one entry for each row.

(The second input could also be a character vector, one character for each row, or a categorical array. It could also be a vector of string objects, one for each row. But it cannot be a cell array of strings.)

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Walter Roberson 2017-7-7

在 MATLAB Online 中打开

y1 = [x1; x2; x3; x4; x5; x6];
cl1 = ones(size(y1));
y2 = [x7; x8; x9; x10; x11; x12];
cl2 = 2 * ones(size(y2));
data = [y1;y2];
data_class = [cl1; cl2];
scattermat(data, data_class)

Ameer Hamza 2018-11-6

How can i pass the data when i have 3 classes w1, w2 and w3 with three feature vectors each i.e x1,x2,x3 and each feature vector has 10 samples ? Guide please

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