Estimation of the median potential followup time.

The reverse Kaplan-Meier method estimates the median potential followup time.

Usage

followup(formula, cens.code = 0, data, ...)

Arguments

formula: A formula whose left hand side is a Hist or a Surv object specifying the event time and the event type where by default 0=censored, 1=event, 2=competing risk (if any). Use cens.code to change the value for censored.
cens.code: Value of the event
data: A data.frame in which all the variables of formula can be interpreted.
...: Arguments passed to prodlim.quantile.

Value

The estimated median potential followup time with inter quartile ranges.

Details

This is merely a wrapper for prodlim with argument reverse.

References

Michael Schemper and Terry L. Smith. A note on quantifying follow-up in studies of failure time. Controlled Clinical Trials, 17(4):343–346, 1996.

Author

Thomas A. Gerds <[email protected]>

Examples

set.seed(8)
d <- SimCompRisk(117)

# overall
followup(Hist(time,event)~1,data=d)
#> Median and inter quartile range (IQR) of the potential follow up time based on the reverse Kaplan-Meier method.
#> Key: <X>
#>          X      Median (IQR)
#>     <char>            <char>
#> 1: Overall 8.22 (4.61;11.46)

# in strata defined by variable X1 
followup(Hist(time,event)~X1,data=d)
#> Median and inter quartile range (IQR) of the potential follow up time based on the reverse Kaplan-Meier method.
#> Key: <X1>
#>       X1      Median (IQR)
#>    <num>            <char>
#> 1:     0    8.42 (7.65;--)
#> 2:     1 7.35 (4.04;10.12)