vegtrans               package:labdsv               R Documentation

_V_e_g_e_t_a_t_i_o_n _T_r_a_n_s_f_o_r_m_a_t_i_o_n _a_n_d _S_t_a_n_d_a_r_d_i_z_a_t_i_o_n

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

     Transforms vegetation abundances according to an arbitrary
     specified vector, or standardize to sample sum or species max.

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

     vegtrans(x,a,b)
     stdveg(x,pltsum=NULL,spcmax=NULL)

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

       x: the original vegetation data.frame

       a: the set of values appearing in the original data.frame

       b: the set of respective values to substitute

  pltsum: standardize by plot sum if TRUE

  spcmax: standardize by species maximum if TRUE

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

     Performs a respective substitution to transform specific values in
     an initial data.frame to other specified values, or standardizes 
     the values.

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

     a data.frame of transformed vegetation

_N_o_t_e:

     Vegetation data are often collected in arbitrary abundance schemes
     (e.g. Braun-Blanquet, Domin, etc. which have no direct algebraic 
     transformation (e.g. log).  This function transforms coded
     abundances to  arbitrary importance values as specified.

     Many ecologist find that standardizing vegetation data improves
     the  performance of some ordination or classification techniques. 
     Using function 'stdveg' with i'pltsum=TRUE' divides all values in
     a sample by the sum of values for that sample, which eliminates
     the effect of differeing productivity or estimation bias in the
     subsecquent analyses.

     Using function 'vegstd' with 'spcmax=TRUE' divides each values by
     the maximum values observed in the data set for that species.  
     This has the effect of making all species equally important in
     subsequent  analyses.

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

     David W. Roberts droberts@montana.edu <URL:
     http://ecology.msu.montana.edu/labdsv>

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

     <URL: http://ecology.montana.msu.edu/labdsv/>

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

     '\linl[vegan]{decostand}', 'wisconsin'

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

         data(bryceveg)
         old <- c(0.2,0.5,1.0,2.0,3.0,4.0,5.0,6.0)
         new <- c(0.2,0.5,3.0,15.0,37.5,62.5,85.0,97.5)
         newveg <- vegtrans(bryceveg,old,new)

