filter.select           package:wavethresh           R Documentation

_P_r_o_v_i_d_e _w_a_v_e_l_e_t _f_i_l_t_e_r _c_o_e_f_f_i_c_i_e_n_t_s.

_D_e_s_c_r_i_p_t_i_o_n:

     This function stores the filter coefficients necessary for doing a
     discrete wavelet transform (and its inverse).

_U_s_a_g_e:

     filter.select(filter.number, family="DaubLeAsymm", constant=1)

_A_r_g_u_m_e_n_t_s:

filter.number: This selects the desired filter, an integer that takes a
          value dependent upon the family that you select.

  family: This selects the basic family that the wavelet comes from.
          The choices are *DaubExPhase* for Daubechies' extremal phase
          wavelets, *DaubLeAsymm* for Daubechies' ``least-asymmetric''
          wavelets, \bolf{Lawton} for Lawton's complex-valued wavelets,
          *LittlewoodPaley* for a bad approximation to Littlewood-Paley
          wavelets.

constant: This constant is applied as a multiplier to all the
          coefficients. It can be a vector, and so you can adapt the
          filter coefficients to be whatever you want. (This is feature
          of negative utility, or ``there is less to this than meets
          the eye'' as my old PhD supervisor would say [GPN]).

_D_e_t_a_i_l_s:

     This function contains at least three types of filter. Two types
     can be selected with family set to DaubExPhase, these wavelets are
     the Haar wavelet (selected by filter.number=1 within this family)
     and Daubechies ``extremal phase'' wavelets selected by
     filter.numbers ranging from 2 to 10). Setting family to
     DaubLeAsymm gives you Daubechies least asymmetric wavelets, but
     here the filter number ranges from 4 to 10. For Daubechies
     wavelets, filter.number corresponds to the N of that paper, the
     wavelets become more regular as the filter.number increases, but
     they are all of compact support. 

     Setting family equal to ``Lawton'' chooses complex-valued
     wavelets. The only wavelet available is the one with
     ``filter.number'' equal to 3. 

     The function 'compare.filters' can be used to compare two filters.

_V_a_l_u_e:

     Alist is returned with four components describing the filter: 

       H: A vector containing the filter coefficients.

       G: A vector containing filter coefficients (if Lawton wavelets
          are selected, otherwise this is NULL).

    name: A character string containing the name of the filter.

  family: A character string containing the family of the filter.

filter.number: The filter number used to select the filter from within
          a family.

_R_E_L_E_A_S_E:

     Version 3.5.3 Copyright Guy Nason 1994

_N_o_t_e:

     The (Daubechies) filter coefficients should always sum to sqrt(2).
     This is a useful check on their validity.

_S_e_e _A_l_s_o:

     'wd', 'wr', 'wr.wd', 'accessC', 'accessD', 'compare.filters',
     'imwd', 'imwr', 'threshold', 'draw'.

_E_x_a_m_p_l_e_s:

     #This function is usually called by others. However, on occasion you may wish to look at the coefficients themselves.

     #
     # look at the filter coefficients for N=4 (by default Daubechies'
     # least-asymmetric wavelets.)
     #
     #filter.select(4)
     #$H:
     #[1] -0.07576571 -0.02963553  0.49761867  0.80373875  0.29785780
     #[6] -0.09921954 -0.01260397  0.03222310
     #
     #$G:
     #NULL
     #
     #$name:
     #[1] "Daub cmpct on least asymm N=4"
     #
     #$family:
     #[1] "DaubLeAsymm"
     #
     #$filter.number:
     #[1] 4

