Getting started


What is the broken stick model?

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

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.

What are the main model assumptions?

The main assumptions of the broken stick model are:

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 (\(Z\)) scale.

Why should I want to use the broken stick model?

Three unique features of the broken stick model are:

What is in the package?

The brokenstick package contains functions to fit, predict and plot data. See the reference page for an overview.


Development of the brokenstick package was kindly supported by the Healthy Birth Growth and Development knowledge integration (HBGDki) program of the Bill & Melinda Gates Foundation.

Further reading