

exists {base}                                R Documentation

_I_s _a_n _O_b_j_e_c_t _D_e_f_i_n_e_d_?

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

     Search for an R object of the given name on the search
     path.

_U_s_a_g_e_:

     exists(x, where = NULL, envir = sys.frame(sys.parent()),
            frame = NULL, mode = "any", inherits = TRUE)

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

       x: a variable name (given as a character string).

where, envir, frame: an environment to be searched.  By
          default this is the environment where the call to
          `envir' takes place.

    mode: the type of interest for the object.

inherits: should the enclosing frames of the environment be
          inspected.

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

     This function looks to see if the name `x' has a value
     bound to it.  If `inherits' is `TRUE' and a value is
     not found for `x', then the parent frames of `envir'
     are searched until the name `x' is encountered. Warn-
     ing: This is the default behaviour for R but not for S.

     If `mode' is specified then only objects of that mode
     are sought.  The function returns `TRUE' if the vari-
     able is encountered and `FALSE' if not.

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

     `get'.

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

     ##  Define a substitute function if necessary:
     if(!exists("some.fun", mode="function"))
      some.fun <- function(x) { cat("some.fun(x)\n"); x }
     search()
     exists("ls", 2) # true even though ls is in pos=3
     exists("ls", 2, inherits=F) # false

