accessD.wd3D           package:wavethresh           R Documentation

_G_e_t _w_a_v_e_l_e_t _c_o_e_f_f_i_c_i_e_n_t_s _f_r_o_m _3_D _w_a_v_e_l_e_t _o_b_j_e_c_t

_D_e_s_c_r_i_p_t_i_o_n:

     This function extracts and returns arrays of wavelet coefficients,
     corresponding to a particular resolution level, from a 'wd'
     wavelet decomposition object.

     The pyramid of coefficients in a wavelet decomposition (returned
     from the 'wd3D' function, say) are packed into a single array in
     'WaveThresh3'.

_U_s_a_g_e:

     accessD.wd3D(obj, level = nlevels(obj)-1, block, ...)

_A_r_g_u_m_e_n_t_s:

     obj: 3D Wavelet decomposition object from which you wish to
          extract the wavelet coefficients.

   level: The resolution level at which you wish to extract
          coefficients. The minimum level you can enter is 0, the
          largest is one less than the number of nlevels stored in the
          obj object.

   block: if block is missing then a list containing all of the wavelet
          coefficient blocks GGG, GGH, GHG, GHH, HGG, HGH, HHG (and
          HHH, if level=0) is returned. Otherwise block should be one
          of the character strings GGG, GGH, GHG, GHH, HGG, HGH, HHG
          and then only that sub-block is returned from the resolution
          level specified.

     ...: any other arguments

_D_e_t_a_i_l_s:

     The need for this function is a consequence of the pyramidal
     structure of Mallat's algorithm and the memory efficiency gain
     achieved by storing the pyramid as a array. 

     Note that this functiOn is a method for the generic function
     'accessD'.

_V_a_l_u_e:

     If the block is missing then a list is returned containing all the
     sub-blocks of coefficients for the specificed resolution 'level'.

     Otherwise the block character string specifies which sub-block of
     coefficients to return.

_R_E_L_E_A_S_E:

     Version 3.9.6 Copyright Guy Nason 1997

_S_e_e _A_l_s_o:

     'link{accessD}', 'link{print.wd3D}', 'link{putD.wd3D}', 
     'link{putDwd3Dcheck}',  'link{summary.wd3D}', 
     'link{threshold.wd3D}',  'link{wd3D}',  'link{wd3D object}', 
     'link{wr3D}'.

_E_x_a_m_p_l_e_s:

     #
     # Generate some test data
     #
     #a <- array(rnorm(8*8*8), dim=c(8,8,8))
     #
     # Perform the 3D DWT
     #
     #awd3D <- wd3D(a)
     #
     # How many levels does this object have?
     #
     #nlevels(awd3D)
     # [1] 3
     #
     # So conceivably we could access levels 0, 1 or 2.
     #
     # Ok. Let's get the level 1 HGH sub-block coefficients:
     #
     #accessD(awd3D, level=1, block="HGH")
     #
     #, , 1
     #           [,1]      [,2] 
     #[1,]  0.8359289 1.3596832
     #[2,] -0.1771688 0.2987303
     #
     #, , 2
     #           [,1]       [,2] 
     #[1,] -1.2633313 1.00221652
     #[2,] -0.3004413 0.04728019
     #
     # This was a 3D array of dimension size 2 (8 -> 4 -> 2, level 3, 2 and then 1)
     #
     #
     # Let's do the same call except this time don't specify the block arg.
     #
     #alllev1 <- accessD(awd3D, level=1)
     #
     # This new object should be a list containing all the subblocks at this level.
     # What are the components?
     #
     #names(alllev1)
     #[1] "GHH" "HGH" "GGH" "HHG" "GHG" "HGG" "GGG"
     #
     # O.k. Let's look at HGH again
     #
     #alllev1$HGH
     #
     #, , 1
     #           [,1]      [,2] 
     #[1,]  0.8359289 1.3596832
     #[2,] -0.1771688 0.2987303
     #
     #, , 2
     #           [,1]       [,2] 
     #[1,] -1.2633313 1.00221652
     #[2,] -0.3004413 0.04728019
     #
     # Same as before.
     #

