vb_convert_freq

 Convert sampling frequency
 y = vb_convert_freq(x, fs, fs2);
 x : [channel x time x trial]
 fs  : original sampling frequency
 fs2 : new sampling frequency
 !! For downsampling, 
    lowpass filtering should be done before using this

 Copyright (C) 2011, ATR All Rights Reserved.
 License : New BSD License(see VBMEG_LICENSE.txt)

0001 function y = vb_convert_freq(x,fs,fs2);
0002 % Convert sampling frequency
0003 % y = vb_convert_freq(x, fs, fs2);
0004 % x : [channel x time x trial]
0005 % fs  : original sampling frequency
0006 % fs2 : new sampling frequency
0007 % !! For downsampling,
0008 %    lowpass filtering should be done before using this
0009 %
0010 % Copyright (C) 2011, ATR All Rights Reserved.
0011 % License : New BSD License(see VBMEG_LICENSE.txt)
0012 
0013 [N,T,Nr]=size(x);
0014 
0015 if fs==fs2;
0016     y=x;
0017 elseif mod(fs,fs2)==0;
0018     y=x(:,1:fs/fs2:T,:);
0019 else
0020     xi  = 1:T;
0021     xii = 1:fs/fs2:T;
0022     TY  = length(xii);
0023     y   = zeros(N,TY,Nr);
0024     
0025     for i=1:N;
0026         y(i,:,:)=interp1(xi,x(i,:,:),xii);
0027     end;
0028 end;