NEWS

brokenstick 0.55 - 06MAY17
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ADDED   New utility functions: get_pev()
CHANGED get_knots() gets a `what` argument
CHANGED smarter defaults for plot()
CHANGED simplified arguments to plot()
CHANGD  much simplified "Overview of main functions" vignette

brokenstick 0.54 - 03MAY17
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ADDED   Support for ggplot
CHANGED Made ggplot plot default
CHANGED Changed default `show_references` flag to FALSE


brokenstick 0.53 - 26APR17
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This is the version announced during my invited lecture at the
7th Channel Network Conference, Hasselt, Belgium.

Here is the abstract of the lecture:

Broken stick model for individual growth curves

Stef van Buuren

1) Netherlands Organization for Applied Scientific Research TNO
2) Utrecht University

The broken stick model describes a set of individual curves by a linear mixed model using first order linear B-splines. The model can be used

- to smooth growth curves by a series of connected straight lines;
- to align irregularly observed curves to a common age grid;
- to create synthetic curves at a user-specified set of break ages;
- to estimate the time-to-time correlation matrix;
- to predict future observations.

The user specifies a set of break ages at which the straight lines connect. Each individual obtains an estimate at each break age, so the set of estimates of the individual form a smoothed version of the observed trajectory.

The main assumptions of the broken stick model are that the development between the break ages follows a straight line, and that the broken stick estimates follow a common multivariate normal distribution. In order to conform to the assumption of multivariate normality, the user may fit the broken stick model on suitably transformed data that yield the standard normal (Z-score) scale.

This lecture outlines the model and introduces the brokenstick R package.