log                   package:base                   R Documentation

_L_o_g_a_r_i_t_h_m_s _a_n_d _E_x_p_o_n_e_n_t_i_a_l_s

_D_e_s_c_r_i_p_t_i_o_n:

     'log' computes natural logarithms, 'log10' computes common (i.e.,
     base 10) logarithms, and 'log2' computes binary (i.e., base 2)
     logarithms. The general form 'logb(x, base)' computes logarithms
     with base 'base'.

     'log1p(x)' computes log(1+x) accurately also for |x| << 1 (and
     less accurately when x is approximately -1).

     'exp' computes the exponential function.

     'expm1(x)' computes exp(x) - 1 accurately also for |x| << 1.

_U_s_a_g_e:

     log(x, base = exp(1))
     logb(x, base = exp(1))
     log10(x)
     log2(x)

     exp(x)
     expm1(x)

     log1p(x)

_A_r_g_u_m_e_n_t_s:

       x: a numeric or complex vector.

    base: positive number.  The base with respect to which logarithms
          are computed.  Defaults to e='exp(1)'.

_D_e_t_a_i_l_s:

     'exp' and 'log' are generic functions: methods can be defined for
     them individually or via the 'Math' group generic.

     'log10' and 'log2' are only special cases, but will be computed
     more efficiently and accurately where supported by the OS.

_V_a_l_u_e:

     A vector of the same length as 'x' containing the transformed
     values.  'log(0)' gives '-Inf' (when available).

_N_o_t_e:

     'log' and 'logb' are the same thing in R, but 'logb' is preferred
     if 'base' is specified, for S-PLUS compatibility.

_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. (for 'log', '\log10' and
     'exp'.)

     Chambers, J. M. (1998) _Programming with Data. A Guide to the S
     Language_. Springer. (for 'logb'.)

_S_e_e _A_l_s_o:

     'Trig', 'sqrt', 'Arithmetic'.

_E_x_a_m_p_l_e_s:

     log(exp(3))
     log10(1e7)# = 7

     x <- 10^-(1+2*1:9)
     cbind(x, log(1+x), log1p(x), exp(x)-1, expm1(x))

