R: 'brokenstick': A package for irregular longitudinal data.

brokenstick-pkg {brokenstick}

R Documentation

brokenstick: A package for irregular longitudinal data.

Description

The broken stick model describes a set of individual curves by a linear mixed model using second-order linear B-splines. The main use of the model is to align irregularly observed data to a user-specified grid of break ages.

Details

The brokenstick package contains functions for fitting a broken stick model to data, for predicting broken stick curves for new data, and for plotting the results.

brokenstick functions

The main functions are:

`brokenstick()`	Fit a broken stick model to irregular data
`plot()`	Plot observed and fitted trajectories by group
`predict()`	Obtain predictions on new data
`summary()`	Extract object summaries

The following functions are user-oriented helpers:

`coef()`	Extract estimated parameters
`fitted()`	Calculate fitted values
`get_knots()`	Obtain the knots from a broken stick model
`get_omega()`	Extract variance-covariance of random effects
`get_r2()`	Obtain proportion of explained variance
`model.frame()`	Extract model frame
`model.matrix()`	Extract design matrix
`residuals()`	Extract residuals from broken stick model

The following functions perform calculations:

`set_control()`	Set controls to steer calculations
`control_kr()`	Set controls for the `kr` method

Note

This work was supported by the Bill & Melinda Gates Foundation. The contents are the sole responsibility of the authors and may not necessarily represent the official views of the Bill & Melinda Gates Foundation or other agencies that may have supported the primary data studies used in the present study.

References

van Buuren, S. (2023). Broken Stick Model for Irregular Longitudinal Data. Journal of Statistical Software, 106(7), 1–51. doi:10.18637/jss.v106.i07