ellip                 package:signal                 R Documentation

_E_l_l_i_p_t_i_c _o_r _C_a_u_e_r _f_i_l_t_e_r

_D_e_s_c_r_i_p_t_i_o_n:

     Generate an Elliptic or Cauer filter (discrete and contnuious).

_U_s_a_g_e:

     ## Default S3 method:
     ellip(n, Rp, Rs, W, type = c("low", "high", "stop",
     "pass"), plane = c("z", "s"), ...)

     ## S3 method for class 'FilterOfOrder':
     ellip(n, Rp = n$Rp, Rs = n$Rs, W = n$Wc, type = n$type, ...)

_A_r_g_u_m_e_n_t_s:

       n: filter order or generic filter model

      Rp: dB of pass band ripple 

      Rs: dB of stop band ripple 

       W: critical frequencies of the filter. 'W' must be a scalar for
          low-pass and high-pass filters, and 'W' must be a two-element
          vector 'c(low, high)' specifying the lower and upper bands.
          For digital filters, 'W' must be between 0 and 1 where 1 is
          the Nyquist frequency.

    type: Filter type, one of '"low"' for a low-pass filter, '"high"'
          for a high-pass filter, '"stop"' for a stop-band
          (band-reject) filter, or '"pass"' for a pass-band filter. 

   plane: '"z"' for a digital filter or '"s"' for an analog filter. 

     ...: additional arguments passed to 'ellip', overriding those
          given by 'n' of class 'FilterOfOrder'. 

_D_e_t_a_i_l_s:

     Because 'ellip' is generic, it can be extended to accept other
     inputs, using '"ellipord"' to generate filter criteria for
     example.

_V_a_l_u_e:

     An 'Arma' object with list elements: 

       b: moving average (MA) polynomial coefficients 

       a: autoregressive (AR) polynomial coefficients 

_A_u_t_h_o_r(_s):

     Original Octave version by Paulo Neis p_neis@yahoo.com.br.
     Modified by Doug Stewart. Conversion to R by Tom Short.

_R_e_f_e_r_e_n_c_e_s:

     Oppenheim, Alan V., Discrete Time Signal Processing, Hardcover,
     1999.

     Parente Ribeiro, E., Notas de aula da disciplina TE498 - 
     Processamento  Digital de Sinais, UFPR, 2001/2002.

     <URL: http://en.wikipedia.org/wiki/Elliptic_filter>

     Octave Forge <URL: http://octave.sf.net>

_S_e_e _A_l_s_o:

     'Arma', 'filter', 'butter', 'cheby1', and 'ellipord'

_E_x_a_m_p_l_e_s:

       # compare the frequency responses of 5th-order Butterworth and elliptic filters.
       bf = butter(5, 0.1)
       ef = ellip(5, 3, 40, 0.1)
       bfr = freqz(bf)
       efr = freqz(ef)
       plot(bfr$f, 20 * log10(abs(bfr$h)), type = "l", ylim = c(-50, 0),
            xlab = "Frequency, radians", ylab = c("dB"))
       lines(efr$f, 20 * log10(abs(efr$h)), col = "red")

