print.survfit            package:survival            R Documentation

Print a Short Summary of a Survival Curve

Description:

     Print number of observations, number of events, the restricted
     mean survival and its standard error, and the median survival with
     confidence limits for the median.

Usage:

     ## S3 method for class 'survfit':
     print(x, scale=1,digits = max(options()$digits - 4,
     3), print.n=getOption("survfit.print.n"), show.rmean=getOption("survfit.print.mean"),...)

Arguments:

       x: the result of a call to the 'survfit' function. 

 print.n: What to use for number of subjects (see below)

  digits: Number of digits to print

   scale: a numeric value to rescale the survival time, e.g., if the
          input data to survfit were in days, 'scale=365' would scale
          the printout to years. 

show.rmean: Show the restricted mean survival?

     ...: other unused arguments

Details:

     The restricted mean ('rmean') and its standard error 'se(rmean)'
     are based on a truncated estimator.  If the last observation(s) is
     not a death, then the survival curve estimate does not go to zero
     and the mean survival time cannot be estimated. Instead, the
     quantity reported is the mean of survival restricted to the time
     before the last censoring. When the last censoring time is not
     random this quantity is occasionally of interest.

     Any randomness in the last censoring time is not taken into
     account in computing the standard error of the restricted mean. 
     The restricted mean is available mainly for compatibility with S,
     and is not shown by default.

     The median and its confidence interval are defined by drawing a
     horizontal line at 0.5 on the plot of the survival curve and its
     confidence bands. The intersection of the line with the lower CI
     band defines the lower limit for the median's interval, and
     similarly for the upper band.  If any of the intersections is not
     a point, then we use the smallest point of intersection, e.g., if
     the survival curve were exactly equal to 0.5 over an interval. 

     The "number of observations" is not well-defined for counting
     process data. Previous versions of this code used the number at
     risk at the first time point. This is misleading if many
     individuals enter late or change strata. The original S code for
     the current version uses the number of records, which is
     misleading when the counting process data actually represent a
     fixed cohort with time-dependent covariates.

     Four possibilities are provided, controlled by 'print.n' or by
     'options(survfit.print.n)': '"none"' prints 'NA', '"records"'
     prints the number of records, '"start"' prints the number at the
     first time point and '"max"' prints the maximum number at risk.
     The initial default is '"start"'.

Value:

     'x', with the invisible flag set.

Side Effects:

     The number of observations (see Details), the number of events, 
     the median survival with its confidence interval, and optionally
     the restricted mean survival ('rmean') and its standard error, are
     printed.  If there are multiple curves, there is one line of
     output for each.

See Also:

     'summary.survfit', 'survfit.object', 'survfit'

Examples:

     ##effect of print.n and show.rmean

     a<-coxph(Surv(start,stop,event)~age+strata(transplant),data=heart)
     b<-survfit(a)
     print(b,print.n="none")
     print(b,print.n="records")
     print(b,print.n="start")
     print(b,print.n="max")
     print(b,show.rmean=TRUE)

