yearmon                 package:zoo                 R Documentation

_A_n _I_n_d_e_x _C_l_a_s_s _f_o_r _M_o_n_t_h_l_y _D_a_t_a

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

     '"yearmon"' is a class for representing monthly data.

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

     yearmon(x)

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

       x: numeric (interpreted as being "in years").

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

     The yearmon class is used to represent monthly data. Internally it
     holds the data as year plus 0 for January, 1/12 for February, 2/12
     for March and so on in order that its internal representation is
     the same as  'ts' class with 'frequency = 12'. If 'x' is not in
     this format it is rounded via 'floor(12*x + .0001)/12'.

     There are coercion methods available for various classes
     including: default coercion to '"yearmon"' (which coerces to
     '"numeric"' first) and coercion from '"yearmon"' to '"Date"' (see
     below), '"POSIXct"', '"POSIXlt"', '"numeric"', '"character"'.  In
     the case of 'as.yearmon.character' the 'format' argument is the
     same as for '"Date"' plus one can have a format specifying a year
     and month but no day.

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

     Returns its argument converted to class 'yearmon'.

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

     'yearqtr', 'zoo', 'zooreg', 'ts'

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

     x <- yearmon(2000 + seq(0, 23)/12)
     x

     as.yearmon("mar07", "%b%y")
     as.yearmon("2007-03-01")

     # returned Date is the fraction of the way through
     # the period given by frac (= 0 by default)
     as.Date(x)
     as.Date(x, frac = 1)
     as.POSIXct(x)

     z <- zoo(rnorm(24), x, frequency = 12)
     z
     as.ts(z)

