butter                package:signal                R Documentation

_G_e_n_e_r_a_t_e _a _B_u_t_t_e_r_w_o_r_t_h _f_i_l_t_e_r.

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

     Generate Butterworth filter polynomial coefficients.

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

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

     ## S3 method for class 'FilterOfOrder':
     butter(n, ...)

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

       n: filter order or generic filter model

       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 'butter', overriding those
          given by 'n' of class 'FilterOfOrder'. 

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

     Because 'butter' is generic, it can be extended to accept other
     inputs, using '"buttord"' 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 Paul Kienzle pkienzle@user.sf.net.
     Modified by Doug Stewart. Conversion to R by Tom Short.

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

     Proakis & Manolakis (1992). Digital Signal Processing. New York:
     Macmillan Publishing Company.

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

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

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

     'Arma', 'filter', 'cheby1', 'ellip', and 'buttord'

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

       bf = butter(4, 0.1)
       freqz(bf)
       zplane(bf)

