\name{addNrisk}

\alias{addNrisk}

\title{Add number-at-risk annotations to a plot}

\description{

Add number-at-risk (NAR) annotations to an existing survival plot, underneath the X-axis.

}

\usage{

addNrisk(x, at = axTicks(1), 

         line = 4, hadj = 0.5, 

         title = "Number at risk", title.adj = 0, 

         labels, hoff = 5, col = 1)

}

\arguments{

  \item{x}{A list as returned by \code{\link{survfit}}.}

  \item{at}{Time points at which the NAR values are calculated and placed.}

  \item{line}{Number of lines into the margin to start displaying the NAR. }

  \item{hadj}{Horizontal adjustment for the NAR values.}

  \item{title}{Optional title above the NAR.}

  \item{title.adj}{Text adjustment for the title}

  \item{labels}{Labels for each stratum.}

  \item{hoff}{Horizontal offset for the labels}

  \item{col}{Color for each stratum.}

}

\details{

This function was written and documented by Aron Charles Eklund in his package

survplot version 0.0.7.

}

\value{Invisibly, a matrix containing the number-at-risk values}

\author{Aron Charles Eklund (survplot version 0.0.7)}

\seealso{

See \code{\link{nrisk}} to retrieve number-at-risk values without plotting them.

See also \code{\link{survplot}}.

}

\examples{

library(survival)

s <- Surv(colon$time / 365, colon$status)

## Need to increase margins a bit

par(mar = c(10,6,2,1))

## no stratification

fit1 <- survfit(s ~ 1)

plot(fit1)

addNrisk(fit1)

## with stratification

fit2 <- survfit(s ~ rx, data = colon)

plot(fit2, xlab = 'Time (years)', ylab = 'Survival')

addNrisk(fit2)

}

\keyword{ survival }

\keyword{ aplot }