• Report

Visualization of categorical longitudinal and times series data

Citation

Tueller, S., Van Dorn, R., & Bobashev, G. (2016). Visualization of categorical longitudinal and times series data. (RTI Press Publication No. MR-0033-1602). Research Triangle Park, NC: RTI Press. DOI: 10.3768/rtipress.2016.mr.0033.1602

Abstract

Plotting growth curves is a powerful graphical approach used in exploratory data analysis for continuous longitudinal data. However, plotting growth curves for multiple participants rapidly becomes uninterpretable with categorical data. Categorical data defines specific states (e.g. being single, married, divorced). And these states do not necessarily need to represent any hierarchical order. Thus a trajectory becomes a sequence of states rather than a continuum. We introduce a horizontal line plot that uses shade or color to differentiate between states on a categorical longitudinal variable for multiple participants. With appropriate sorting, stacking the horizontal lines representing each participant can reveal important patterns such as the shape of, or heterogeneity in, the trajectories. We illustrate the plotting techniques for large sample sizes, observed groups, the exploration of unobserved latent classes, large numbers of time points such as are found with intensive longitudinal designs or multivariate time series data, individually varying times observation, unique numbers of observations, and missing data. We used the R package longCatEDA to create the illustrations. Illustrative data include both simulated data and alcohol consumption data in adult schizophrenics from the Clinical Antipsychotic Trials of Intervention Effectiveness.

Author Details

Stephen Tueller

Stephen J. Tueller, PhD, is a Quantitative Psychologist at RTI International. His research interests are graphical exploratory data analysis, latent variable mixture modeling, simulation methodologies, and measurement invariance in multiple group models.

Richard Van Dorn

Richard A. Van Dorn, PhD, is a Senior Mental Health Services Researcher at RTI International. His research focuses on the evaluation of longitudinal substance use and mental health outcomes for adults with mental illnesses.

Georgiy Bobashev

Georgiy V. Bobashev, PhD, is a senior research statistician and an expert in biostatistics methodology and mathematical modeling. His current research interests cover two major areas: substance-use studies and predictive modeling. In the substance-use research area, he focuses on personalized treatments and a systems approach to addictions. In predictive modeling, he focuses on methods development in forecasting health outcomes, predominantly substance use and risky behavior.