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sample

PURPOSE ^

Random sampling of points from a data-set

SYNOPSIS ^

s=sample(A,m,r)

DESCRIPTION ^

 SAMPLE  Random sampling of points from a data-set 
  
  CALL: s = sample(data,m,R) 
    
   s    = sampled selection from data,  size m x D 
   data = data matrix, size N x D (D = # dimensions) 
   m    = sampling size  
   R    = 0 sampling without replacement  
          1 sampling with replacement (default) 
   
   SAMPLE(DATA,M,R) selects a random sample of M data points from the 
   multivariate data-set in the matrix DATA. 
  
  Example: 
      data = wnormrnd(0,1,500,3); 
      s    = sample(data,100,0)

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

001 function s=sample(A,m,r) 
002 %SAMPLE  Random sampling of points from a data-set 
003 % 
004 % CALL: s = sample(data,m,R) 
005 %   
006 %  s    = sampled selection from data,  size m x D 
007 %  data = data matrix, size N x D (D = # dimensions) 
008 %  m    = sampling size  
009 %  R    = 0 sampling without replacement  
010 %         1 sampling with replacement (default) 
011 %  
012 %  SAMPLE(DATA,M,R) selects a random sample of M data points from the 
013 %  multivariate data-set in the matrix DATA. 
014 % 
015 % Example: 
016 %     data = wnormrnd(0,1,500,3); 
017 %     s    = sample(data,100,0) 
018 % 
019  
020 % History: 
021 % revised pab dec2003   
022 %  changed ind generation to avoid dependence on stats-toolbox 
023 % revised pab 10.12.1999 
024 %  - faster sampling 
025 % by CB kdetools 
026  
027 if nargin<2, 
028   error('Incorrect number of function parameters'); 
029 end; 
030 if nargin<3 |isempty(r) 
031  r=1; 
032 end 
033  
034 [n d]=size(A); 
035  
036 if m>n & r==0, 
037   error('Requested sample size too large'); 
038 end; 
039  
040 if m==n & r==0, 
041   s=A; 
042   return; 
043 end; 
044  
045 if r==0, % Sample without replacement. 
046  ind = randperm(n); 
047 else  % sample with replacement 
048  ind = ceil(n*rand(m,1)); 
049 end 
050 s=A(ind(1:m),:);  
051

Mathematical Statistics
Centre for Mathematical Sciences
Lund University with Lund Institute of Technology

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