survival (version 2.34-1)

print.survfit: 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

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.

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".

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)