Surv                package:survival5                R Documentation

_C_r_e_a_t_e _a _S_u_r_v_i_v_a_l _O_b_j_e_c_t

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

     Create a survival object, usually used as a response variable in a
     model formula.

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

     Surv(time, event)
     or
     Surv(time, time2, event, type=<<see below>>, origin=0)
     is.Surv(x)

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

    time: for right censored data, this is the follow up time.  For
          interval data, the first argument is the starting time for
          the interval. 

       x: any S-PLUS object. 

   event: The status indicator, normally 0=alive, 1=dead.  Other
          choices are T/F (TRUE = death) or 1/2 (2=death). For interval
          censored data, the status indicator is 0=right censored, 1=
          event at `time', 2=left censored, 3=interval censored.
          Although unusual, the event indicator can be omitted, in
          which case all subjects are assumed to have an event. 

   time2: ending time of the interval for interval censored  or
          counting process  data only.  Intervals are assumed to be
          open on the left and closed on the right, `(start, end]'. For
          counting process data, `event' indicates whether an event
          occurred at the end of the interval. 

    type: character string specifying the type of censoring. Possible
          values are `"right"', `"left"', `"counting"', `"interval"',
          or `"interval2"'. The default is `"right"' or `"counting"'
          depending on whether the `time2' argument is absent or
          present, respectively. 

  origin: for counting process data, the hazard function origin.  This
          is most often used in conjunction with a model containing
          time dependent strata in order to align the subjects properly
          when they cross over from one strata to another. 

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

     An object of class `Surv'.  There are methods for `print',
     `is.na', and subscripting survival objects.  To include a survival
     object inside a data frame, use the `I()' function.  `Surv'
     objects are implemented as a matrix of 2 or 3 columns.

     In the case of `is.Surv', a logical value `T' if `x' inherits from
      class `"Surv"', otherwise an `F'.

_D_E_T_A_I_L_S:

     In theory it is possible to represent interval censored data
     without a third column containing the explicit status.  Exact,
     right censored, left censored and interval censored observation
     would be represented as intervals of (a,a), (a, infinity),
     (-infinity,b), and (a,b) respectively; each specifying the
     interval within which the event is known to have occurred.

     If `type = "interval2"' then the representation given above is
     assumed, with NA taking the place of infinity.  If
     `type="interval" `event' must be given.  If `event' is `0', `1',
     or `2', the relevant information is assumed to be contained in
     `time', the value in `time2' is ignored, and the second column of
     the result will contain a placeholder.

     Presently, the only methods allowing interval censored data are
     the parametric models computed by `survreg',  so the distinction
     between open and closed intervals is unimportant.   The
     distinction is important for counting process data and the Cox
     model.

     The function tries to distinguish between the use of 0/1 and 1/2
     coding for left and right censored data using `if
     (max(status)==2)'. If 1/2 coding is used and all the subjects are
     censored, it will guess wrong.  Use 0/1 coding in this case.

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

     data(aml)
     Surv(aml$time, aml$status)

