axTicks                 package:base                 R Documentation

_C_o_m_p_u_t_e _A_x_i_s _T_i_c_k_m_a_r_k _L_o_c_a_t_i_o_n_s

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

     Compute tickmark locations, the same way as R does internally.
     This is only non-trivial when log coordinates are active. By
     default, gives the `at' values which `axis(side)' would use.

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

     axTicks(side, axp = NULL, usr = NULL, log = NULL)

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

    side: integer in 1:4, as for `axis'.

     axp: numeric vector of length three, defaulting to `par("Zaxp")'
          where ``Z'' is ``x'' or ``y'' depending on the `side'
          argument.

     usr: numeric vector of length four, defaulting to `par("usr")'
          giving horizontal (`x') and vertical (`y') user coordinate
          limits.

     log: logical indicating if log coordinates are active; defaults to
          `par("Zlog")' where `Z' is as for the `axp' argument above.

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

     The `axp', `usr', and `log' arguments must be consistent as their
     default values (the `par(..)' results) are. Note that the meaning
     of `axp' alters very much when `log' is `TRUE', see the
     documentation on `par(xaxp=.)'.

     `axTicks()' can be regarded as an R implementation  of the C
     function `CreateAtVector()' in `..../src/main/graphics.c' which is
     called by `axis(side,*)' when no argument `at' is specified.

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

     numeric vector of coordinate values at which axis tickmarks can be
     drawn.  By default, when only the first argument is specified,
     these values should be identical to those that `axis(side)' would
     use or has used.

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

     `axis',`par'.

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

      plot(1:7, 10*21:27)
      axTicks(1)
      axTicks(2)
      stopifnot(identical(axTicks(1), axTicks(3)),
                identical(axTicks(2), axTicks(4)))

     ## Show how axTicks() and axis() correspond :
     op <- par(mfrow = c(3,1))
     for(x in 9999*c(1,2,8)) {
         plot(x,9, log = "x")
         cat(formatC(par("xaxp"),wid=5),";",T <- axTicks(1),"\n")
         rug(T, col="red")
     }
     par(op)

