Dear R-users,
I'd like to announce the release of the new version of package JM (soon
available from CRAN) for the joint modelling of longitudinal and
time-to-event data using shared parameter models. These models are
applicable in mainly two settings. First, when focus is in the
time-to-event outcome and we wish to account for the effect of a
time-dependent covariate measured with error. Second, when focus is in
the longitudinal outcome and we wish to correct for nonrandom dropout.
New features include:
* function survfitJM() has been added that calculates predictions of
subject-specific survival probabilities given a history of longitudinal
responses.
* function dynC() has been added that calculates a dynamic
concordance index for joint models. The function also returns
time-dependent areas under the ROC curve.
* method = "ch-GH" has been replaced by method =
"spline-PH-GH" that
fits a relative risk model with a B-spline-approximated baseline risk
function. Similarly to method = "ch-GH", the plan is that the same
relative risk model with a B-spline-approximated baseline risk will also
replace method = "ch-Laplace".
* method = "spline-PH-GH" allows for stratification, i.e.,
different
spline coefficients are estimated for the different levels of a
stratification factor. By default the knots positions are the same
across strata -- this can be changed by either directly specifying the
knots or by setting the control argument 'equal.strata.knots' to FALSE.
* the new function wald.strata() can be used to test for equality of
the spline coefficients among strata.
* jointModel() has now the extra argument 'lag' that allows for
lagged effects in the time-dependent covariate represented by the linear
mixed model.
* method = "ph-GH" that fits a relative risk with an unspecified
baseline risk function has been renamed to method = "Cox-PH-GH".
* a bug was corrected in joint models with piecewise constant
baseline risk function. In particular, the 'xi' parameters were reported
as double their actual value.
As always, any kind of feedback (e.g., questions, suggestions,
bug-reports, etc.) is more than welcome.
Best,
Dimitris
--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014
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