yearqtr                 package:zoo                 R Documentation

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

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

     '"yearqtr"' is a class for representing quarterly data.

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

     yearqtr(x)
     as.yearqtr(x, ...)
     ## S3 method for class 'yearqtr':
     format(x, format = "%Y Q%q", ...)

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

       x: for 'yearqtr' a numeric (interpreted as being  "in years"). 
          For 'as.yearqtr' another date class object.  For the
          '"yearqtr"' method of 'format' an  object of class
          '"yearqtr"' or if called as 'format.yearqtr' then an object
          with an 'as.yearqtr' method that can be coerced  to
          '"yearqtr"'.

  format: character string specifying format. '"%C"', '"%Y"', '"%y"'
          and '"%q"', if present, are replaced with the century, year,
          last two digits of the year,  and quarter (i.e. a number
          between 1 and 4), respectively.

     ...: other arguments.  Currently not used.

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

     The yearqtr class is used to represent quarterly data. Internally
     it holds the data as year plus 0 for Quarter 1, 1/4 for Quarter 2
     and so on in order that its internal representation is the same as
      'ts' class with 'frequency = 4'. If 'x' is not in this format it
     is rounded via 'floor(4*x + .0001)/4'.

     'as.yearqtr.character' uses a default format of '"%Y Q%q"',  '"%Y
     q%q"' or '"%Y-%q"' according to whichever matches. '%q' accepts
     the numbers 1-4 (possibly with leading zeros).

     There are coercion methods available for various classes
     including: default coercion to '"yearqtr"' (which coerces to
     '"numeric"' first) and coercion from '"yearqtr"' to '"Date"' (see
     below), '"POSIXct"', '"POSIXlt"', '"numeric"', '"character"'.

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

     'yearqtr' and 'as.yearqtr' return the first argument converted to 
     class 'yearqtr'. The 'format' method returns a character string
     representation of its argument first argument.

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

     'yearmon', 'zoo', 'zooreg', 'ts', code{strptime}.

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

     x <- yearqtr(2000 + seq(0, 7)/4)
     x

     format(x, "%Y Quarter %q")
     as.yearqtr("2001 Q2")
     as.yearqtr("2001 q2") # same
     as.yearqtr("2001-2") # same

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

     zz <- zoo(rnorm(8), x, frequency = 4)
     zz
     as.ts(zz)

