sdpar-methods              package:dti              R Documentation

_M_e_t_h_o_d_s _f_o_r _F_u_n_c_t_i_o_n _s_d_p_a_r _i_n _P_a_c_k_a_g_e _d_t_i

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

     This function estimates the parameters of a piecewise linear model
     for  the dependence between error standard deviation and mean.

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

       ## S4 method for signature 'dtiData':
       sdpar(object,level=NULL,sdmethod="sd",interactive=TRUE)

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

  object: An object of class 'dtiData' 

   level: Suggested value for slot 'level'. As a default the value in
          'object@level' is used. The value determines the lower
          endpoint of the linear section in the model for error
          standard deviation as a function of the mean.

sdmethod: Method for estimating voxelwise standard deviations if
          replicates of zero weighted images are available, either
          '"sd"' or '"mad"'.

interactive: If 'TRUE' a density of values in zero weighted images is
          plotted together with  the specification of the lower
          endpoint of the interval of linearity. A good choice of this
          point should correspond, if present, to the minimum between
          the first two modes of the density estimate. The value can be
          changed or accepted. If changed a new value for slot 'lambda'
          is set. 

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

     The function returns an object of class 'dtiData'.

_M_e_t_h_o_d_s:



     _o_b_j = "_A_N_Y" Returns a warning 

     _o_b_j = "_d_t_i_D_a_t_a" Estimate parameters of a model for the dependence
          between error standard deviation and mean.


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

     Karsten Tabelow tabelow@wias-berlin.de
       J\"org Polzehl polzehl@wias-berlin.de

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

     'dtiData', 'readDWIdata', 'dti.smooth',  'dtiTensor',

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

       ## Not run: demo(dti_art)

