question about val.surv in R

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Please specify the package(s) you are using.  In this case it should be rms.

val.surv is mainly for an out-of-sample validation, as it does not penalize
for overfitting.  calibrate.cph is probably what you should be using.

To use val.surv in the fashion you are trying to use it, specify y=TRUE,
surv=TRUE to cph and specify the time point you are validating with the u
argument to val.surv (e.g., u=1 for 1 year survival probability validation).

Frank
Dear R users:

I tried to use val.surv to give an internal validation of survival
prediction model.

I used the sample sources.

# Generate failure times from an exponential distribution
set.seed(123)              # so can reproduce results
n <- 1000
age <- 50 + 12*rnorm(n)
sex <- factor(sample(c('Male','Female'), n, rep=TRUE, prob=c(.6, .4)))
cens <- 15*runif(n)
h <- .02*exp(.04*(age-50)+.8*(sex=='Female'))
t <- -log(runif(n))/h
units(t) <- 'Year'
label(t) <- 'Time to Event'
ev <- ifelse(t <= cens, 1, 0)
t <- pmin(t, cens)
S <- Surv(t, ev)

# I use cph instead of psm in the example
f <- cph(S ~ age + sex, y=TRUE)
w <- val.surv(f)

I got an error:
Error in survreg.distributions[[fit$dist]] :
  attempt to select less than one element

Could some one explain for me?

Error in survreg.distributions[[fit$dist]] :
  attempt to select less than one element

Error in survreg.distributions[[fit$dist]] :
  attempt to select less than one element

*Yao Zhu*
*Department of Urology
Fudan University Shanghai Cancer Center
Shanghai, China*

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-----
Frank Harrell
Department of Biostatistics, Vanderbilt University
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