Grant Foster wrote a number of the routines (or precursor routines) used in VStar many years ago when he worked at AAVSO. His book, Analyzing Light Curves a Practical Guide, published in 2010 is the best text I have found with the clearest explanations of what the Various analytical methods in VStar are doing and how to choose parameter settings when using them and how to interpret results. It is not a user manual for VStar. it doesn't tell you how the VStar user interface works. In fact it references "R" packages and routines in many cases. R is a free, open-source extremely powerful - perhaps the most powerful - statistical language and programming environment and is used extensively in the pharmaceutical industry and astronomy.
The references to R do not detract from the clear explanations of how to go about various types of analyses, how they work and how to correctly interpret results. You just have to know that VStar doesn't necessarily do all of the things that are available in the enormous number of functions and packages available for free in R. VStar is powerful and has the advantage of an extremely simple and intuitive user interface.
The book was not available in 2020 when I ran the last session of the CHOICE course Analyzing Data with VStar due to most Lulu publishing operations shutting down in the early stages of the pandemic. Grant graciously provided a PDF version free of charge for distribution to registered course participants. I checked this morning and it is once again available from Lulu publishing for about US$11.00 at
If you are a serious VStar user but not a master statistician, I strongly recommend you keep this book by your computer when using VStar.
My copy of this book is well used by now. :)
Grant Foster's R code for DCDFT, AoV, ANOVA and other functions are here:
VStar's implementation of DCDFT and WWZ (the latter not included in the R codes zip) were ported from Fortran code by Matthew Templeton which were in turn ported from BASIC code by Grant.
R and Python are now widely used in scientific computing generally (I use them almost daily, and others such as C/C++ and Fortran less frequently), and choosing between them is not straightforward. If VStar had been written now, it would very likely have used one of these. :) It's worth noting that when Grant wrote his initial VSTAR code for DOS, I'm fairly sure it was in BASIC (Elizabeth, Sara?) and by the time he had written his book, he was using R. See also https://app.aavso.org/media/jaavso/2881.pdf
Grant's R code (dcdft, peak1 functions) has been used recently when verifying my implementation of period uncertainty (https://github.com/AAVSO/VStar/issues/255, https://github.com/AAVSO/VStar/issues/256).