# Surv

##### Create a Survival Object

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

- Keywords
- survival

##### Usage

```
Surv(time, event)
or
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.
- 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 unu - 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 o - type
- character string specifying the type of censoring. Possible values
are
`"right"`

,`"left"`

,`"counting"`

,`"interval"`

, or`"interval2"`

. The default is`"right"`

or`"counting"`

- 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. 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`

.

##### synopsis

Surv(time,time2,event,type,origin)

##### DETAILS

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

##### Examples

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

*Documentation reproduced from package survival, version 2.11-4, License: GPL2*