survreg               package:survival               R Documentation

Regression for a Parametric Survival Model

Description:

     Regression for a parametric survival model. These are all
     time-transformed location models, with the most useful case being
     the accelerated failure models that use a log transformation.

Usage:

     survreg(formula=formula(data), data=parent.frame(), weights, 
     subset,na.action,dist="weibull",  init=NULL, scale=0,
      control=survreg.control(),parms=NULL,model=FALSE, x=FALSE,
      y=TRUE, robust=FALSE, ...)

Arguments:

 formula: a formula expression as for other regression models. See the
          documentation for 'lm' and 'formula' for details. 

    data: optional data frame in which to interpret the variables
          occurring in the formula. 

 weights: Optional observation weights

  subset: subset of the observations to be used in the fit. 

na.action: function to be used to handle any NAs in the data. 

    dist: assumed distribution for y variable.

          If the argument is a character string, then it is assumed to
          name an element from 'survreg.distributions'. These include
          '"weibull"', '"exponential"', '"gaussian"', '"logistic"',
          '"lognormal"' and '"loglogistic"'. Only enough of the name
          needs to be given to make the choice unique.

          Otherwise, it is assumed to be a user defined list conforming
          to the format described in 'survreg.distributions'. 

   parms: a list of fixed parameters.  For the t-distribution for
          instance this is the degrees of freedom; most of the
          distributions have no parameters. 

    init: optional vector of initial values for the parameters. 

   scale: optional fixed value for the scale.  If set to <=0 then the
          scale is estimated. 

 control: a list of control values, in the format producted by
          'survreg.control'. 

   model: if TRUE, the model frame is returned. 

       x: if TRUE, then the X matrix is returned. 

       y: if TRUE, then the y vector (or survival times) is returned. 

  robust: if TRUE, sandwich standard errors are computed. Defaults to
          TRUE when 'formula' contains a 'cluster' term. 

     ...: other arguments which will be passed to 'survreg.control'. 

Value:

     an object of class 'survreg' is returned.

Compatibility note:

     This routine underwent significant changes from survival4 to
     survival5. The survreg.old function gives a backwards-compatible
     interface.  In S-PLUS the new function is called 'survReg' and the
     old one 'survreg'.

See Also:

     'survreg.object', 'survreg.distributions', 'pspline', 'frailty',
     'ridge', 'survreg.old'

Examples:

     ## These are all the same
     survreg(Surv(futime, fustat) ~ ecog.ps + rx, ovarian, dist='weibull',scale=1)
     survreg(Surv(futime, fustat) ~ ecog.ps + rx, ovarian,
     dist="exponential")
     survreg.old(Surv(futime, fustat) ~ ecog.ps + rx, ovarian, dist='extreme',fixed=list(scale=1),link="log")

