I set out reading this book hoping to understand the metaprogramming chapter, and ended up learning a bunch of other stuff along the way! Here’s a non-exhaustive list of things I learned from each of the sections of Advanced R:
I - Foundations:
- I notice that I use the switch function a ton now, where previously I used if-else nests.
- I use condition-handling to pass errors back to the user of my Shiny apps now.
- I now know what an Environment is and where and why R would look for something. (This helps both in function-writing and debugging!)
- I write a heck of a lot of functions (this ties into II: Functional Programming, of course)
II - Functional Programming
- I map the crap out of everything now (if I didn’t before, it’s way worse now!), and have learned to use functions in a ton of different ways.
- I now understand what a function factory is, and what to do if a function somehow returns me a function instead (as opposed to panicking about it!)
- I now know about a series of modifiers to help adjust function behaviours (memoise, quietly, safely, possibly) - although I use tryCatch as much as I do these.
III - OOP
- I wrote a package that uses S3! It’s cool to minimize the user interface for multiple platforms and the mental load accompanying.
- I still lean to using the explicit “switch” function a lot instead of writing out a useMethod call. May be a habit/pattern worth breaking in the future.
- I’m now comfortable USING an R6 package - I don’t know that I’d reach for an R6 system now but the whole “function$method” thing doesn’t scare me anymore
- S4? wot that
V Techniques
- Debugging: I now know how to use browser, and love it! Also debug()!
- Performance measure/improve: still don’t do a ton of this, even though I’m a shiny dev. I feel like I should care more but I mostly work with smaller data (sub 1,000,000 rows) right now.
- I … still don’t know C++ or Rcpp. 🤷
Toy Code
Metaprogramming - how to pass expressions into select statements. Also example of switch.
library(dplyr)
library(rlang)
grouping_variables <- switch(
params$group_type,
"S" = exprs(CraftCode, starts_with("Product"), ModelCode, Elevation),
"B" = exprs(starts_with("Rate")),
"P" = exprs(starts_with("Part"))
)
null_bids <- bids %>%
group_by(SupplierID, ProjectID, !!!grouping_variables) %>%
slice_max(LastModDate) %>%
ungroup() %>%
select(!!!grouping_variables, ProjectID, SupplierAID, SupplierName, UnitPrice) %>%
left_join(lowest_bids, by = as.character(grouping_variables))