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??

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

[Jan]

The author of this code was not interested in others using his code. Otherwise he had inserted some comments which explain the usage. The readers of the forum could guess, what is wanted as input. But this is not the clean way of using foreign code reliably.

[Sayed Afreen]

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]

@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.

Answer 1

[Walter Roberson]

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.)

[Sayed Afreen]

Thank you so much..

[Sayed Afreen]

If I take the input of 12 vectors and each represent one sample,and I separate the vectors into two classes like y1 and y2,in y1 the 6 vectors from x1 to x6 and y2 consist of next 6 vectors i.e.x7 to x12 then how could I pass this as the parameter to this function.

[Walter Roberson]

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]

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