counter_sim.m Illustrates that there is no theoretical difference between counter.m and randperm. Randperm is faster

0001 % counter_sim.m 0002 % 0003 % Illustrates that there is no theoretical difference between counter.m and 0004 % randperm. Randperm is faster 0005 % 0006 % 0007 0008 % 11/24/03 Petr Janata 0009 0010 ntrials = 20; 0011 ncond = 4; 0012 total_trials = ncond*ntrials; 0013 0014 % Create a list of 4 conditions, 20 trials each 0015 fprintf('Creating design matrix with randperm ...\n'); 0016 X = reshape(ones(ntrials,1)*(1:ncond),total_trials,1); 0017 0018 % Create a dummy coded matrix with conditions in columns. Randomize assignment 0019 % of condition to each trial using randperm 0020 X = full(sparse(1:total_trials,X(randperm(total_trials)),1)); 0021 0022 % Eliminate the 4th condition 0023 X(:,ncond) = []; 0024 0025 % Create a similar matrix using counter.m for the randomization 0026 fprintf('Creating desing matrix with counter ...\n'); 0027 [c] = counter(ncond, ntrials*ncond); 0028 0029 Y = full(sparse(1:total_trials,c,1)); 0030 Y(:,ncond) = []; 0031 0032 % Now dump the correlation matrix for each design matrix 0033 0034 fprintf('Correlation matrix generated using randperm:\n') 0035 corrcoef(X) 0036 0037 fprintf('\nCorrelation matrix generated using counter:\n') 0038 corrcoef(Y)

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