Find time points that signal changes to the given integer bit pattern
only specified bits are examined and other bits are ignored
by taking bitwise AND
ix = vb_bit_ptn_start(y,status)
ix = vb_bit_ptn_start(y,status,t_stay)
y : event signal
status : integer defined by bit pattern
= 2^n : correspond to check n-th bit
t_stay : minimum length to stay the specified value [default = 10]
'y' should be stay at the value 'status' for more than t_stay
ix : index corresponding to the start point
'y' changes to 'status' from other value
2009-6-11 Masa-aki Sato
2012-1-8 Masa-aki Sato Bug fix
Copyright (C) 2011, ATR All Rights Reserved.
License : New BSD License(see VBMEG_LICENSE.txt)0001 function ix = vb_bit_ptn_start(y,status,t_stay) 0002 % Find time points that signal changes to the given integer bit pattern 0003 % only specified bits are examined and other bits are ignored 0004 % by taking bitwise AND 0005 % ix = vb_bit_ptn_start(y,status) 0006 % ix = vb_bit_ptn_start(y,status,t_stay) 0007 % y : event signal 0008 % status : integer defined by bit pattern 0009 % = 2^n : correspond to check n-th bit 0010 % t_stay : minimum length to stay the specified value [default = 10] 0011 % 'y' should be stay at the value 'status' for more than t_stay 0012 % 0013 % ix : index corresponding to the start point 0014 % 'y' changes to 'status' from other value 0015 % 0016 % 2009-6-11 Masa-aki Sato 0017 % 2012-1-8 Masa-aki Sato Bug fix 0018 % 0019 % Copyright (C) 2011, ATR All Rights Reserved. 0020 % License : New BSD License(see VBMEG_LICENSE.txt) 0021 0022 if nargin < 3, t_stay = 10; end; 0023 0024 T = length(y); 0025 0026 % take bitwise AND to ignore irrelevant bit 0027 y = bitand(y,status); 0028 0029 flg = ones(1,T-t_stay); 0030 tt = 1:T-t_stay; 0031 0032 % 'y' is not 'status' value beforehand 0033 flg = flg .* (y(tt) ~= status); 0034 0035 % 'y' should be stay at the value 'status' for more than t_stay 0036 for t=1:t_stay 0037 flg = flg .* (y(tt + t) == status); 0038 end 0039 0040 ix = find(flg == 1); 0041 0042 return