reorder.factor             package:gdata             R Documentation

_R_e_o_r_d_e_r _t_h_e _L_e_v_e_l_s _o_f _a _F_a_c_t_o_r

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

     Reorder the levels of a factor

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

     ## S3 method for class 'factor':
     reorder(x,
                              X,
                              FUN,
                              ...,
                              order=is.ordered(x),
                              new.order,
                              sort=mixedsort)

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

       x: factor

       X: auxillary data vector

     FUN: function to be applied to subsets of 'X' determined by 'x',
          to determine factor order

     ...: optional parameters to 'FUN'

   order: logical value indicating whether the returned object should
          be an 'ordered' factor

new.order: a vector of indexes or a vector of label names giving the
          order of the new factor levels

    sort: function to use to sort the factor level names, used only
          when 'new.order' is missing

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

     This function changes the order of the levels of a factor. It can
     do so via three different mechanisms, depending on whether, 'X'
     _and_ 'FUN', 'new.order' or 'sort' are provided.

     If 'X' _and_ 'Fun' are provided: The data in 'X' is grouped by the
     levels of 'x' and 'FUN' is applied. The groups are then sorted by
     this value, and the resulting order is used for the new factor
     level names.

     If 'new.order' is provided: For a numeric vector, the new factor
     level names are constructed by reordering the factor levels
     according to the numeric values. For vectors, 'new.order' gives
     the list of new factor level names. In either case levels omitted
     from 'new.order' will become missing ('NA') values.

     If 'sort' is provided (as it is by default): The new factor level
     names are generated by applying the supplied function to the
     existing factor level names. With 'sort=mixedsort' the factor
     levels are sorted so that combined numeric and character strings
     are sorted in according to character rules on the character
     sections (including ignoring case), and the numeric rules for the
     numeric sections. See 'mixedsort' for details.

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

     A new factor with reordered levels

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

     Gregory R. Warnes warnes@bst.rochester.edu

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

     'factor' and 'reorder'

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

        # Create a 4 level example factor
        trt <- factor( sample( c("PLACEBO", "300 MG", "600 MG", "1200 MG"),
                       100, replace=TRUE ) )
        summary(trt)
        # Note that the levels are not in a meaningful order.

        # Change the order to something useful
        # default "mixedsort" ordering
        trt2 <- reorder(trt)
        summary(trt2)
        # using indexes:
        trt3 <- reorder(trt, new.order=c(4, 2, 3, 1))
        summary(trt3)
        # using label names:
        trt4 <- reorder(trt, new.order=c("PLACEBO", "300 MG", "600 MG", "1200 MG"))
        summary(trt4)
        # using frequency
        trt5 <- reorder(trt, X=as.numeric(trt), FUN=length)
        summary(trt5)

        # drop out the '300 MG' level
        trt6 <- reorder(trt, new.order=c("PLACEBO", "600 MG", "1200 MG"))
        summary(trt6)

