\name{psm}
\alias{psm}
\alias{print.psm}
\alias{Hazard}
\alias{Survival}
\alias{Hazard.psm}
\alias{Mean.psm}
\alias{Quantile.psm}
\alias{Survival.psm}
\alias{residuals.psm}
\alias{lines.residuals.psm.censored.normalized}
\alias{survplot.residuals.psm.censored.normalized}
\title{
Parametric Survival Model
}
\description{

  \code{psm} is a modification of Therneau's \code{survreg} function for
  fitting the accelerated failure time family of parametric survival
  models.  \code{psm} uses the \code{Design} class for automatic
  \code{anova}, \code{fastbw}, \code{calibrate}, \code{validate}, and
  other functions.  \code{Hazard.psm}, \code{Survival.psm},
  \code{Quantile.psm}, and \code{Mean.psm} create S functions that
  evaluate the hazard, survival, quantile, and mean (expected value)
  functions analytically, as functions of time or probabilities and the
  linear predictor values.

The \code{residuals.psm} function exists mainly to compute normalized
(standardized) residuals and to censor them (i.e., return them as
\code{Surv} objects) just as the original failure time variable was
censored.  These residuals are useful for checking the underlying
distributional assumption (see the examples).  To get these residuals,
the fit must have specified \code{y=TRUE}.  A \code{lines} method for these
residuals automatically draws a curve with the assumed standardized
survival distribution.  A \code{survplot} method runs the standardized
censored residuals through \code{survfit} to get Kaplan-Meier estimates,
with optional stratification (automatically grouping a continuous
variable into quantiles) and then through \code{survplot.survfit} to plot
them.  Then \code{lines} is invoked to show the theoretical curve.  Other
types of residuals are computed by \code{residuals} using
\code{residuals.survreg}.

Older versions of \code{survreg} used by \code{psm} (e.g., on S-Plus
2000) had the following additional arguments \code{method, link, parms,
  fixed}.  See \code{\link{survreg}} on such systems for details.
\code{psm} passes those arguments to \code{survreg}.
}
\usage{
psm(formula=formula(data),
    data=if (.R.) parent.frame() else sys.parent(), weights,
    subset, na.action=na.delete, dist="weibull",
    init=NULL, scale=0, 
    control=if(!.R.) survReg.control() else survreg.control(),
    parms=NULL, 
    model=FALSE, x=FALSE, y=TRUE, time.inc, \dots)
# dist=c("extreme", "logistic", "gaussian", "exponential", 
#        "rayleigh", "t")      for S-Plus before 5.0
# dist=c("extreme", "logistic", "gaussian", "weibull",
#        "exponential", "rayleigh", "lognormal",
#        "loglogistic" "t")    for R, S-Plus 5,6
# Older versions had arguments method, link, parms, fixed

\method{print}{psm}(x, correlation=FALSE, \dots)

Hazard(object, \dots)
\method{Hazard}{psm}(object, \dots)   # for psm fit
# E.g. lambda <- Hazard(fit)

Survival(object, \dots)
\method{Survival}{psm}(object, \dots) # for psm
# E.g. survival <- Survival(fit)

\method{Quantile}{psm}(object, \dots) # for psm
# E.g. quantsurv <- Quantile(fit)

\method{Mean}{psm}(object, \dots)     # for psm
# E.g. meant   <- Mean(fit)

# lambda(times, lp)   # get hazard function at t=times, xbeta=lp
# survival(times, lp) # survival function at t=times, lp
# quantsurv(q, lp)    # quantiles of survival time
# meant(lp)           # mean survival time

\method{residuals}{psm}(object, type="censored.normalized", \dots)

\method{survplot}{residuals.psm.censored.normalized}(fit, x, g=4, col, main, \dots)

\method{lines}{residuals.psm.censored.normalized}(x, n=100, lty=1, xlim,
lwd=3, \dots)
# for type="censored.normalized"
}
\arguments{
\item{formula}{
an S statistical model formula. Interactions up to third order are
supported. The left hand side must be a \code{Surv} object.
}
\item{object}{a fit created by \code{psm}.  For \code{survplot} with
  residuals from \code{psm}, \code{object} is the result of
  \code{residuals.psm}.
}
\item{fit}{a fit created by \code{psm}}
\item{data}{}
\item{subset}{}
\item{weights}{}
\item{dist}{}
\item{scale}{}
\item{init}{}
\item{na.action}{}
\item{control}{see \code{survreg} (\code{survReg} for S-Plus 5. or 6.).
  \code{fixed} is used for S-Plus before 5., \code{parms} is used for
  S-Plus 5, 6, and \R.  See \code{cph} for \code{na.action}. 
}
\item{parms}{a list of fixed parameters.  For the \eqn{t}-distribution
  this is the degrees of freedom; most of the distributions have no
  parameters.}
\item{model}{
set to \code{TRUE} to include the model frame in the returned object
}
\item{x}{
set to \code{TRUE} to include the design matrix in the object produced
by \code{psm}.  For the \code{survplot} method, \code{x} is an optional
stratification variable (character, numeric, or categorical).  For
\code{lines.residuals.psm.censored.normalized}, \code{x} is the result
of \code{residuals.psm}.  For \code{print} it is the result of \code{psm}.
}
\item{y}{
set to \code{TRUE} to include the \code{Surv()} matrix
}
\item{time.inc}{
setting for default time spacing. Used in constructing time axis
in \code{survplot}, and also in make confidence bars. Default is 30
if time variable has \code{units="Day"}, 1 otherwise, unless
maximum follow-up time \eqn{< 1}. Then max time/10 is used as \code{time.inc}.
If \code{time.inc} is not given and max time/default \code{time.inc} is
\eqn{> 25}, \code{time.inc} is increased.
}
\item{correlation}{set to \code{TRUE} to print the correlation matrix
  for parameter estimates}
\item{\dots}{
other arguments to fitting routines, or to pass to \code{survplot} from
\cr
\code{survplot.residuals.psm.censored.normalized}.  Ignored for
\code{lines}.}
\item{times}{
a scalar or vector of times for which to evaluate survival probability
or hazard
}
\item{lp}{
a scalar or vector of linear predictor values at which to evaluate
survival probability or hazard.  If both \code{times} and \code{lp} are
vectors, they must be of the same length.
}
\item{q}{
a scalar or vector of probabilities.  The default is .5, so just the
median survival time is returned.  If \code{q} and \code{lp} are both vectors,
a matrix of quantiles is returned, with rows corresponding to \code{lp}
and columns to \code{q}.
}
\item{type}{
type of residual desired.  Default is censored normalized residuals,
defined as (link(Y) - linear.predictors)/scale parameter, where the
link function was usually the log function.  See \code{survreg} for other
types (\code{survReg} for S-Plus 6).
}
\item{n}{
number of points to evaluate theoretical standardized survival
function for 
\cr
\code{lines.residuals.psm.censored.normalized}
}
\item{lty}{
line type for \code{lines}, default is 1
}
\item{xlim}{
range of times (or transformed times) for which to evaluate the standardized
survival function.  Default is range in normalized residuals.
}
\item{lwd}{
line width for theoretical distribution, default is 3
}
\item{g}{
number of quantile groups to use for stratifying continuous variables
having more than 5 levels
}
\item{col}{
vector of colors for \code{survplot} method, corresponding to levels of \code{x}
(must be a scalar if there is no \code{x})
}
\item{main}{
main plot title for \code{survplot}.  If omitted, is the name or label of
\code{x} if \code{x} is given.  Use \code{main=""} to suppress a title when you
specify \code{x}.
}}
\value{
\code{psm} returns a fit object with all the information \code{survreg} would store as 
well as what \code{Design} stores and \code{units} and \code{time.inc}.
\code{Hazard}, \code{Survival}, and \code{Quantile} return S-functions.
\code{residuals.psm} with \code{type="censored.normalized"} returns a \code{Surv} object
which has a special attribute \code{"theoretical"} which is used by the \code{lines}
routine.  This is the assumed standardized survival function as a function
of time or transformed time.
}
\details{
The object \code{survreg.distributions} contains definitions of properties
of the various survival distributions. 
\cr
\code{psm} does not trap singularity errors due to the way \code{survreg.fit}
does matrix inversion.  It will trap non-convergence (thus returning
\code{fit$fail=TRUE}) if you give the argument \code{failure=2} inside the
\code{control} list which is passed to \code{survreg.fit}.  For example, use
\code{f <- psm(S ~ x, control=list(failure=2, maxiter=20))} to allow up to
20 iterations and to set \code{f$fail=TRUE} in case of non-convergence.
This is especially useful in simulation work.
}
\author{
Frank Harrell\cr
Department of Biostatistics\cr
Vanderbilt University
\cr
f.harrell@vanderbilt.edu
}
\seealso{
\code{\link{Design}}, \code{\link{survreg}}, \code{\link{survReg}}, \code{\link{residuals.survreg}}, \code{\link{survreg.object}}, 
\code{\link{survreg.distributions}},
\code{\link{pphsm}}, \code{\link{survplot}}, \code{\link{survest}}, \code{\link[survival]{Surv}},
\code{\link[Hmisc]{na.delete}}, \code{\link[Hmisc]{na.detail.response}}, \code{\link{datadist}}, \code{\link{latex.psm}}
}
\examples{
n <- 400
set.seed(1)
age <- rnorm(n, 50, 12)
sex <- factor(sample(c('Female','Male'),n,TRUE))
dd <- datadist(age,sex)
options(datadist='dd')
# Population hazard function:
h <- .02*exp(.06*(age-50)+.8*(sex=='Female'))
d.time <- -log(runif(n))/h
cens <- 15*runif(n)
death <- ifelse(d.time <= cens,1,0)
d.time <- pmin(d.time, cens)


f <- psm(Surv(d.time,death) ~ sex*pol(age,2), 
         dist=if(.R.)'lognormal' else 'gaussian')
# Log-normal model is a bad fit for proportional hazards data


anova(f)
fastbw(f)  # if deletes sex while keeping age*sex ignore the result
f <- update(f, x=TRUE,y=TRUE)       # so can validate, compute certain resids
validate(f, dxy=TRUE, B=10)      # ordinarily use B=150 or more
plot(f, age=NA, sex=NA)       # needs datadist since no explicit age, hosp.
survplot(f, age=c(20,60))     # needs datadist since hospital not set here
# latex(f)


S <- Survival(f)
plot(f$linear.predictors, S(6, f$linear.predictors),
     xlab=if(.R.)expression(X*hat(beta)) else 'X*Beta',
     ylab=if(.R.)expression(S(6,X*hat(beta))) else 'S(6|X*Beta)')
# plots 6-month survival as a function of linear predictor (X*Beta hat)


times <- seq(0,24,by=.25)
plot(times, S(times,0), type='l')   # plots survival curve at X*Beta hat=0
lam <- Hazard(f)
plot(times, lam(times,0), type='l') # similarly for hazard function


med <- Quantile(f)        # new function defaults to computing median only
lp <- seq(-3, 5, by=.1)
plot(lp, med(lp=lp), ylab="Median Survival Time")
med(c(.25,.5), f$linear.predictors)
                          # prints matrix with 2 columns


# fit a model with no predictors
f <- psm(Surv(d.time,death) ~ 1, dist=if(.R.)"weibull" else "extreme")
f
pphsm(f)          # print proportional hazards form
g <- survest(f)
plot(g$time, g$surv, xlab='Time', type='l',
     ylab=if(.R.)expression(S(t)) else 'S(t)')


f <- psm(Surv(d.time,death) ~ age, 
         dist=if(.R.)"loglogistic" else "logistic", y=TRUE)
r <- resid(f, 'cens') # note abbreviation
survplot(survfit(r), conf='none') 
                      # plot Kaplan-Meier estimate of 
                      # survival function of standardized residuals
survplot(survfit(r ~ cut2(age, g=2)), conf='none')  
                      # both strata should be n(0,1)
lines(r)              # add theoretical survival function
#More simply:
survplot(r, age, g=2)


options(datadist=NULL)
}
\keyword{models}
\keyword{survival}