Surv: Create a Survival Object

Description

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

Usage

Surv(time, time2, event, type =, origin = 0)
is.Surv(x)

Arguments

time

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

any R object.

event

The status indicator, normally 0=alive, 1=dead. Other choices are TRUE/FALSE (TRUE = death) or 1/2 (2=death). For interval censored data, the status indicator is 0=right censored, 1=event at time

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 whethe

type

character string specifying the type of censoring. Possible values
    are "right", "left", "counting",
    "interval", or "interval2".  The default is
    "right" or "cou

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.

`Value`

An object of class Surv.  There are methods for print,
  is.na, and subscripting survival objects.   Surv objects
  are implemented as a matrix of 2 or 3 columns.
  In the case of is.Surv, a logical value TRUE if x
  inherits from class "Surv", otherwise an FALSE.

`Details`

Typical usages are
Surv(time, event)
Surv(time, time2, event, type=, origin=0)
    
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.

`See Also`

coxph, survfit, survreg.

`Examples`

Run this codewith(aml, Surv(time, status))
with(heart, Surv(start,stop,event))
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