functions in filter.i - t

             to_db(signal, ref)  
          or to_db(signal)  
 
     return 20.*log10(abs(SIGNAL)/REF), the number of decibels  
     corresponding to the input SIGNAL.  REF defaults to 1.0.  
interpreted function, defined at i/filter.i   line 510  

             to_phase(signal)  
          or to_phase(signal, 1)  
 
     return atan(SIGNAL.im,SIGNAL.re), the phase of the input SIGNAL.  
     If the second argument is present and non-0, the phase will be in  
     degrees; by default the phase is in radians.  
     To_phase attempts to unroll any jumps from -180 to +180 degrees  
     or vice-versa; zero phase will be taken somewhere near the middle  
     of the signal.  The external variable to_phase_eps controls the  
     details of this unrolling; you can turn off unrolling by setting  
     to_phase_eps=0.0 (initially it is 0.3).  
interpreted function, defined at i/filter.i   line 524