search for: logitudinal

...> This is not my understanding of the terms. To me, both time series and longitudinal data can be regular or irregular, but time series data typically have a lot more measurement points (20 at a minimum) and often has only one or a few "subjects" - e.g. trends in the stock market. Logitudinal data are often collected at fewer time points, but with many subject (e.g. measuring people repeatedly to see if something about them changes over time, and changes differently in different people). Peter Peter L. Flom, PhD Statistical Consultant www DOT peterflomconsulting DOT com