SUATTRIBUTES - trace ATTRIBUTES instantanteous amplitude, phase,	
 		 or frequency						

 suattributes <stdin >stdout mode=amp					

 Required parameters:							
 	none								

 Optional parameter:							
 	mode=amp	output flag 					
 	       		=amp envelope traces				
 	       		=phase phase traces				
 	       		=freq frequency traces				
	unwrap=		default unwrap=0 for mode=phase			
 			default unwrap=1 for mode=freq			
 			dphase_min=PI/unwrap				
	normalize=0		=1 normalize by instantaneous amplitude	 	
	verbose=0	silent =1 chatty				
 Notes:								

 This program performs complex trace attribute analysis, a la Taner,	
 Kohler, and Sheriff, 1979.						

 The unwrap parameter is active only for mode=freq and mode=phase. The	
 quantity dphase_min is the minimum change in the phase angle taken to be
 the result of phase wrapping, rather than natural phase variation in the
 data. Setting unwrap=0 turns off phase-unwrapping altogether. Choosing
 unwrap > 1 makes the unwrapping function more sensitive to phase changes.
 Setting unwrap > 1 may be necessary to resolve higher frequencies in	
 data (or sample data more finely). The phase unwrapping is crude. The 
 differentiation needed to compute the instantaneous frequency		
 freq(t)= d(phase)/dt is a simple centered difference.			

 Examples:								
 suvibro f1=10 f2=50 t1=0 t2=0 tv=1 | suattributes mode=amp | ...	
 suvibro f1=10 f2=50 t1=0 t2=0 tv=1 | suattributes mode=phase | ...	
 suvibro f1=10 f2=50 t1=0 t2=0 tv=1 | suattributes mode=freq | ...	
 suplane | suattributes mode=... | supswigb |...       		


 Credits:
	CWP: Jack Cohen
      CWP: John Stockwell (added freq and unwrap features)

 Algorithm:
	c(t) = hilbert_tranform_kernel(t) convolved with data(t)  

  amp(t) = sqrt( c.re^2(t) + c.im^2(t))
  phase(t) = arctan( c.im(t)/c.re(t))
  freq(t) = d(phase)/dt

 Reference: Taner, M. T., Koehler, A. F., and  Sheriff R. E.
 "Complex seismic trace analysis", Geophysics,  vol.44, p. 1041-1063, 1979

 Trace header fields accessed: ns, trid
 Trace header fields modified: d1, trid