cdt               package:compositions               R Documentation

_C_e_n_t_e_r_e_d _d_e_f_a_u_l_t _t_r_a_n_s_f_o_r_m

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

     Compute the centered default transform of a (dataset of)
     composition or amount.

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

               cdt(x)
               ## Default S3 method:
               cdt( x )
               ## S3 method for class 'acomp':
               cdt( x )
               ## S3 method for class 'rcomp':
               cdt( x )
               ## S3 method for class 'aplus':
               cdt( x )
               ## S3 method for class 'rplus':
               cdt( x )
               ## S3 method for class 'rmult':
               cdt( x )
               ## S3 method for class 'factor':
               cdt( x )
               

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

       x: a classed amount or composition (or a matrix of), to be
          transformed with its centered default transform

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

     The general idea of this package is to analyse the same data with
     different geometric concepts as similar as possible. For each of
     the four concepts there exists a unique transform expressing the
     geometry in a linear subspace, keeping the relation to the
     variables. This unique transformation is computed by 'cdt'. For
     'acomp' the transform is 'clr', for 'rcomp' it is 'cpt', for 
     'aplus' it is 'ilt', and for 'rplus' it is 'iit'. Each component
     of the result is identified with a unit vector in the direction of
     the corresponding component of the original composition or amount.
     Keep in mind that the transform is not necessarily surjective and
     thus variances in the image space might be singular.

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

     A corresponding matrix or vector containing the transforms.

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

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

     'idt', 'clr', 'cpt', 'ilt', 'iit'

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

     ## Not run: 
     # the cdt is defined by
     cdt         <- function(x) UseMethod("cdt",x)
     cdt.default <- function(x) x
     cdt.acomp   <- clr 
     cdt.rcomp   <- cpt 
     cdt.aplus   <- ilt 
     cdt.rplus   <- iit 
     ## End(Not run)
     cdt(acomp(1:5))
     cdt(rcomp(1:5))

