transIPCW: Inverse probability of censoring weighted transition probabilities

Description

Provides estimates for the transition probabilities based on inverse probability of censoring weighted estimators, IPCW.

Usage

transIPCW(object, s, t, x, bw="dpik", window="normal", method.weights="NW",
state.names=c("1", "2", "3"), conf=FALSE, n.boot=1000, conf.level=0.95,
method.boot="percentile", method.est=1, ...)

Arguments

object

An object of class survTP.

The first time for obtaining estimates for the transition probabilities. If missing, 0 will be used.

The second time for obtaining estimates for the transition probabilities. If missing, the maximum of Stime will be used.

Covariate values for obtaining estimates for the conditional transition probabilities. If missing, unconditioned transition probabilities will be computed.

A character string indicating a function to compute a kernel density bandwidth. Defaults to dpik from package KernSmooth. Alternatively a single numeric value can be specified.

window

A character string specifying the desired kernel. See details below for possible options. Defaults to normal where the gaussian density kernel will be used.

method.weights

A character string specifying the desired weights method. Possible options are NW for the Nadaraya-Watson weights and LL for local linear weights. Defaults to NW.

state.names

A vector of characters giving the state names.

conf

Provides pointwise confidence bands. Defaults to FALSE.

n.boot

The number of bootstrap samples. Defaults to 1000 samples.

conf.level

Level of confidence. Defaults to 0.95 (corresponding to 95%).

method.boot

The method used to compute bootstrap confidence bands. Possible options are percentile and basic. Defaults to percentile.

method.est

The method used to compute the estimate. Possible options are 1 or 2.

...

Further arguments. Typically these arguments are passed to the function specified by argument bw.

Value

If argument x is missing or if argument object doesn't contain a covariate, an object of class TPmsm is returned. There are methods for contour, image, print and plot. TPmsm objects are implemented as a list with elements:
methodA string indicating the type of estimator used in the computation.
estA matrix with transition probability estimates. The rows being the event times and the columns the 5 possible transitions.
infA matrix with the lower transition probabilities of the confidence band. The rows being the event times and the columns the 5 possible transitions.
supA matrix with the upper transition probabilities of the confidence band. The rows being the event times and the columns the 5 possible transitions.
timeVector of times where the transition probabilities are computed.
sStart of the time interval.
tEnd of the time interval.
hThe bandwidth used. If the estimator doesn't require a bandwidth, it's set to NULL.
state.namesA vector of characters giving the states names.
n.bootNumber of bootstrap samples used in the computation of the confidence band.
conf.levelLevel of confidence used to compute the confidence band.
If argument x is specified and argument object contains a covariate, an object of class TPCmsm is returned. There are methods for print and plot. TPCmsm objects are implemented as a list with elements:
methodA string indicating the type of estimator used in the computation.
estA 3 dimensional array with transition probability estimates. The first dimension being the event times, the second the covariate values and the last one the 5 possible transitions.
infA 3 dimensional array with the lower transition probabilities of the confidence band. The first dimension being the event times, the second the covariate values and the last one the 5 possible transitions.
supA 3 dimensional array with the upper transition probabilities of the confidence band. The first dimension being the event times, the second the covariate values and the last one the 5 possible transitions.
timeVector of times where the transition probabilities are computed.
covariateVector of covariate values where the conditional transition probabilities are computed.
sStart of the time interval.
tEnd of the time interval.
xAdditional covariate values where the conditional transition probabilities are computed, which may or may not be present in the sample.
hThe bandwidth used.
state.namesA vector of characters giving the states names.
n.bootNumber of bootstrap samples used in the computation of the confidence band.
conf.levelLevel of confidence used to compute the confidence band.

encoding

UTF-8

Details

If bw="dpik" then possible options for argument window are normal, box, epanech, biweight or triweight. When argument bw is numeric then argument window accepts the same options as when bw="dpik" plus one of tricube, triangular or cosine. If method.est=1 then $p_{11}(s,t|X)$, $p_{12}(s,t|X)$ and $p_{22}(s,t|X)$ are estimated according to the following expressions: $p_{11}(s,t|X)=\frac{1-P(Z \leq t|X)}{1-P(Z \leq s|X)}$, $p_{12}(s,t|X)=\frac{P(Z \leq t|X)-P(Z \leq s|X)-P(smethod.est=2 then $p_{11}(s,t|X)$, $p_{12}(s,t|X)$ and $p_{22}(s,t|X)$ are estimated according to the following expressions: $p_{11}(s,t|X)=\frac{P(Z>t|X)}{P(Z>s|X)}$, $p_{12}(s,t|X)=\frac{P(st|X)}{P(Z>s|X)}$, $p_{22}(s,t|X) =\frac{P(Z \leq s,T>t|X)}{P(Z \leq s, T>s|X)}$. Then, $p_{13}(s,t|X)=1-p_{11}(s,t|X)-p_{12}(s,t|X)$ and $p_{23}(s,t|X)=1-p_{22}(s,t|X)$.

References

Meira-Machado L., de Uña-Álvarez J., Datta S. Conditional Transition Probabilities in a non-Markov Illness-death Model. Discussion Papers in Statistics and Operation Research n 11/03, 2011. Department of Statistics and Operations Research, University of Vigo (ISSN: 1888-5756, Deposito Legal VG 1402 - 2007). This file can be downloaded from: http://webs.uvigo.es/depc05/reports/12_05.pdf

Meira Machado L. F., de Uña-Álvarez J., Cadarso-Suárez C. (2006) Nonparametric estimation of transition probabilities in a non-Markov illness-death model. Lifetime Data Anal 12(3), 325--344.

Davison, A. C., Hinkley, D. V. (1997) Bootstrap Methods and their Application Chapter 5, Cambridge University Press.

Examples

Run this code

# Set the number of threads
nth <- setThreadsTP(2)

# Create survTP object with age as covariate
data(heartTP)
heartTP_obj <- with(heartTP, survTP(time1, event1, Stime, event, age=age))

# Compute unconditioned transition probabilities
transIPCW(object=heartTP_obj, s=33, t=412)

# Compute unconditioned transition probabilities with confidence band
transIPCW(object=heartTP_obj, s=33, t=412, conf=TRUE, conf.level=0.9,
method.boot="basic", method.est=2)

# Compute conditional transition probabilities
transIPCW(object=heartTP_obj, s=33, t=412, x=0)

# Compute conditional transition probabilities with confidence band
transIPCW(object=heartTP_obj, s=33, t=412, x=0, conf=TRUE, conf.level=0.95,
n.boot=100, method.boot="percentile", method.est=2)

# Restore the number of threads
setThreadsTP(nth)

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