This is a companion discussion topic for the original entry at https://rviews.rstudio.com/2021/05/14/basic-fda-descriptive-statistics-with-r
In a previous post, I introduced the topic of Functional Data Analysis (FDA). In that post, I provided some background on Functional Analysis, the mathematical theory that makes FDA possible, identified FDA resources that might be of interest R users, and showed how to turn a series of data points into an FDA object. In this post, I will pick up where I left off and move on to doing some very basic FDA descriptive statistics.
Let’s continue with the same motivating example from last time. We will use synthetic data generated by a Brownian motion process and pretend that it is observed longitudinal data. However, before getting to the statistics, I would like to take a tiny, tidy diversion. The functions in fda and other fundamental FDA R packages require data structured in matrices. Consequently, the examples in the basic FDA reference works (listed below) construct matrices using code that seems to be convenient for the occasion. I think this makes adapting sample code to user data a little harder than it needs to be. There ought to be standard data structures for working with FDA data. I propose tibbles or data frames with function values packed into lists.
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