# brokenstick 1.1.1 Unreleased

• Handles an edge case that crashed predict()

# brokenstick 1.1.0 2020-11-02

This version adds a couple of minor alterations.

• Adds a link to the JSS manuscript in the description field
• Removes unnecessary \dontrun{} directives
• Exports parse_formula() to remove ::: from examples
• Sanitises chunk names by removing : and _ characters
• Corrects some “first-order” mindo’s to “second-order”
• Repairs plotting glitch in oldfriends.Rmd
• Limits number of printed rows in predict.brokenstick() example

# brokenstick 1.0.0 Unreleased

• Ready for CRAN –> Move up to version 1.0.0
• The package is now hosted on https://github.com/growthcharts/brokenstick/

# brokenstick 0.78.0 Unreleased

• Prepare package for first CRAN submission

# brokenstick 0.77.0 Unreleased

• Add documentation for the brokenstick class object
• Add JSS manuscript as a vignette
• Remove the prediction vignette and its dependencies
• Extend plot.brokenstick() with the ability to plot imputed trajectories
• Add the weightloss data
• Fail early when user specifies degree > 1

# brokenstick 0.76.0 Unreleased

• Adds argument what to plot.brokenstick()
• Solves a bug that always yielded zero rows for case 3 prediction
• Solves a data combination problem in predict() when the group variable is a factor
• Add a better explanation of the boundary parameter
• Evades that model.matrix() removes rows with NA if degree = 0

# brokenstick 0.75.0 Unreleased

• This version trims down the package in various ways
• Removes dependencies of hardhat and recipes
• Makes the brokenstick object smaller since no blueprints are stored
• Removes the recipe interface to the brokenstick() function
• Moves ggplot2 to suggests
• Copies over the install.on.demand() function from mice

# brokenstick 0.72.1 Unreleased

• Imports recipes::recipe() to inform R package installation process

# brokenstick 0.71.0 Unreleased

• Removes the dependency on growthstandards
• Updates and corrects plot examples
• Tries to evade ggplot2 out-of-range/missing messages through better filtering

# brokenstick 0.70.1 Unreleased

• Adds support for brokenstick model with degree = 0

# brokenstick 0.70.0 Unreleased

• This version jump illustrates big and breaking changes:
1. brokenstick adopted the tidymodels philosophy, and now includes a dependency on hardhat. It is now possible to fit a model using five different interfaces. There is no need anymore the hardcode variable names in the source data.

2. This version introduces a new estimation method, the Kasim-Raudenbush sampler. The new method is more flexible and faster than lme4::lmer() when the number of knots is large.

3. This version introduces two simple correlation models that may be used to smooth out the variance-covariance matrix of the random effects.

4. The definition of the brokenstick class has changed. Objects of class brokenstick do no longer store the training data.

5. The brokenstick_export class is retired.

6. The predict() function is fully rewritten as has now a new interface. Since the brokenstick class does not store the training data anymore, the predict() function now obtains a new_data argument. Syntax that worked for brokenstick package before 0.70.0 does not work anymore and should be updated. The shape argument replaces the output argument.

7. The plot() function is rewritten, and now requires a new_data specification.

8. Retired functions: brokenstick() replaces fit_brokenstick(), predict.brokenstick() replaces predict.brokenstick_export(), get_r2() replaces get_pev()

9. Removed functions: get_data(), get_X(), export()

# brokenstick 0.62.0 Unreleased

• This version simplifies the plotting functions
• Renders ggplot objects sharper in vignettes by svglite
• Drops the pkg argument in plot.brokenstick()
• Lessens the dependency on rbokeh
• Replaces hbgd (which is no longer developed) by growthstandards package
• Replaces smocc_50/fit_50 by smocc_200/fit_200
• Added a NEWS.md file to track changes to the package

# brokenstick 0.61.0 Unreleased

• Added smocc_50 and fit_50 demo data
• Removed smocc.hgtwgt, smocc_hgtwgt and fit_206 datasets
• Adapt code and vignettes to reflect replacement of demo data

# brokenstick 0.60.0 Unreleased

• Adapted source to R 4.0.0.

# brokenstick 0.55 Unreleased

• Added new utility function get_pev() for proportion explained variance
• get_knots() gets a what argument
• Now using smarter defaults for plot()
• Simplified arguments to plot()
• Simplified vignette “Overview of main functions”

# brokenstick 0.54 Unreleased

• Added Support for ggplot2
• Made ggplot2 plot default
• Changed default show_references flag to FALSE

# brokenstick 0.53 Unreleased

• 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 second-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.