expression               package:base               R Documentation

_U_n_e_v_a_l_u_a_t_e_d _E_x_p_r_e_s_s_i_o_n_s

_D_e_s_c_r_i_p_t_i_o_n:

     Creates or tests for objects of mode '"expression"'.

_U_s_a_g_e:

     expression(...)

     is.expression(x)
     as.expression(x, ...)

_A_r_g_u_m_e_n_t_s:

     ...: valid R expressions.

       x: an arbitrary R object.

_V_a_l_u_e:

     'expression' returns a vector of mode '"expression"' containing
     its arguments as unevaluated "calls".

     'is.expression' returns 'TRUE' if 'expr' is an expression object
     and 'FALSE' otherwise.

     'as.expression' attempts to coerce its argument into an expression
     object.

_R_e_f_e_r_e_n_c_e_s:

     Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) _The New S
     Language_. Wadsworth & Brooks/Cole.

_S_e_e _A_l_s_o:

     'call', 'eval', 'function'. Further, 'text' and 'legend' for
     plotting math expressions.

_E_x_a_m_p_l_e_s:

     length(ex1 <- expression(1+ 0:9))# 1
     ex1
     eval(ex1)# 1:10

     length(ex3 <- expression(u,v, 1+ 0:9))# 3
     mode(ex3 [3]) # expression
     mode(ex3[[3]])# call
     rm(ex3)

