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"' and
     '"jul"'.   The last one is from the 'frame' package on CRAN.

     There is an 'is.numeric' method which returns 'FALSE'.

     There is also a 'date' method for 'as.yearqtr' usable with objects
     created with package 'date'.

     'Sys.yearqtr()' returns the current year/month and methods for
     'min', 'max' and 'range' are defined (by defining  a method for
     'Summary'.

     A 'yearqtr' 'mean' method is also defined.

     Certain methods support a 'frac' argument.  See 'yearmon'.

_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', 'strptime'.

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

     x <- as.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)

