is.date                 package:date                 R Documentation

_D_a_t_e _O_b_j_e_c_t_s

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

     Tests for objects of class `"date"'.

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

     is.date(x)
     as.date(x)

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

       x: any R object.

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

     `is.date' returns `TRUE' if `x' has mode `"date"', and `FALSE'
     otherwise.

     Its behavor is unaffected by any attributes of `x'; for example,
     `x' could be a date array (in contrast to the behavior of
     `is.vector').

     `as.date' returns `x' if `x' is a simple object of class `"date"',
     and otherwise a date vector of the same length as `x' and with
     data resulting from coercing the elements of `x' to class
     `"date"'.  See the manual page for `as.date()' for details.

     Dates are stored as the number of days since 1/1/1960, and are
     kept in integer format.  (This is the same baseline value as is
     used by SAS).  The numerical methods for dates treat `date - date'
     as a numeric, and `date +- numeric' as a date.

     Logical operations as well as the numeric functions `exp()',
     `log()', and so on are invalid.

     Other methods exist for missing value, `as.character()', printing,
     and summarizing.

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

     `date.mdy', `mdy.date', `date.ddmmmyy',  `as.date'.

