brolgar: An R package to BRowse Over Longitudinal Data Graphically and Analytically in R

TL;DR

The paper introduces the R package brolgar, which offers graphical and analytical tools to better visualize and understand individual patterns in longitudinal data, overcoming the limitations of traditional spaghetti plots.

Contribution

The novel R package brolgar provides enhanced visualization and analysis features for longitudinal data, facilitating the identification of individual differences beyond hierarchical linear models.

Findings

Improved visualization of individual longitudinal patterns.

Tools for diagnosing and summarizing individual differences.

Enhanced understanding of data beyond traditional models.

Abstract

Longitudinal (panel) data provide the opportunity to examine temporal patterns of individuals, because measurements are collected on the same person at different, and often irregular, time points. The data is typically visualised using a "spaghetti plot", where a line plot is drawn for each individual. When overlaid in one plot, it can have the appearance of a bowl of spaghetti. With even a small number of subjects, these plots are too overloaded to be read easily. The interesting aspects of individual differences are lost in the noise. Longitudinal data is often modelled with a hierarchical linear model to capture the overall trends, and variation among individuals, while accounting for various levels of dependence. However, these models can be difficult to fit, and can miss unusual individual patterns. Better visual tools can help to diagnose longitudinal models, and better capture the individual experiences. This paper introduces the R package, brolgar (BRowse over Longitudinal data Graphically and Analytically in R), which provides tools to identify and summarise interesting individual patterns in longitudinal data.