I can’t really grasp what the ~ means. I understand the concept of the .x and .f more than the ~.
~ is just a signifier
Are you calling a function? Or writing an expression?
The search path
I am confused about the package environment and how they are related when doing search path. Is it a one line relationship starting from global environment to empty environment?
Yes.
It’s a path, not a tree
Order of packages
I’m unsure why tidyverse loads in the order it does. Does it have to do with dependencies between some of the packages in the tidyverse?
I’m not sure either, but…
…yes, I think it has to do with dependencies and functions that mask other functions
rlang is one of the imports of the purrr package, so I think rlang is automatically loaded before purrr when you load the tidyverse first, which would explain why the objects from the tidyverse are still masking those from rlang (since either way, rlang is loaded first)
rlang is a dependency of purrr (Imports field in DESCRIPTION)…
…but library(purrr) does NOT attachrlang!
purrr is a dependency of tidyverse (Imports field in DESCRIPTION)…
… tidyverseattachespurrr, but NOT rlang
This behavior is unusual
Why multiple environments
Why does R need multiple environments? Why can’t the same environment be available to users and developers?
Because otherwise a user’s behavior could affect the way a developer’s code works
Inheritance
Are functions “inherited” from parent environments?
No.
Are other things inherited?
Not exactly, but sort of…
…S3 objects can have multiple classes
Do most environments have just one parent (excluding the empty environment)?
Yes, they all do.
Advice
Common feedback from years past
Use message() instead of print()
Return data, don’t just print messages to console
Think in terms of vectors and data frames, not messages or single values
Build your function to be vectorized!
Code style matters: pay attention to spaces, line breaks, indents, etc.
Use Crtl-I
Why do you love for loops so much?!?!??!?!!
Conditions
Two important concepts
Three types of conditions:
errors
warnings
messages
(Recall R Markdown chunk options!)
Catching errors:
catching errors with tryCatch()
Errors
stop() (or rlang::abort())
Terminates execution immediately
my_filter <-function(x, ...) {if (!"wacky"%in%class(x)) {stop("x is not wacky") } dplyr::filter(x, ...)}class(starwars) <-c("wacky", class(starwars))my_filter(starwars, name =="Chewbacca")
# A tibble: 1 × 14
name height mass hair_color skin_color eye_color birth_year sex gender
<chr> <int> <dbl> <chr> <chr> <chr> <dbl> <chr> <chr>
1 Chewbacca 228 112 brown unknown blue 200 male mascu…
# ℹ 5 more variables: homeworld <chr>, species <chr>, films <list>,
# vehicles <list>, starships <list>
my_filter(dplyr::starwars)
Error in my_filter(dplyr::starwars): x is not wacky
Warnings
warning() (or rlang::warn())
Execution continues
my_filter <-function(x, ...) {if (!"wacky"%in%class(x)) {warning("x is not wacky") } dplyr::filter(x, ...)}my_filter(dplyr::starwars)
Warning in my_filter(dplyr::starwars): x is not wacky
# A tibble: 87 × 14
name height mass hair_color skin_color eye_color birth_year sex gender
<chr> <int> <dbl> <chr> <chr> <chr> <dbl> <chr> <chr>
1 Luke Sk… 172 77 blond fair blue 19 male mascu…
2 C-3PO 167 75 <NA> gold yellow 112 none mascu…
3 R2-D2 96 32 <NA> white, bl… red 33 none mascu…
4 Darth V… 202 136 none white yellow 41.9 male mascu…
5 Leia Or… 150 49 brown light brown 19 fema… femin…
6 Owen La… 178 120 brown, gr… light blue 52 male mascu…
7 Beru Wh… 165 75 brown light blue 47 fema… femin…
8 R5-D4 97 32 <NA> white, red red NA none mascu…
9 Biggs D… 183 84 black light brown 24 male mascu…
10 Obi-Wan… 182 77 auburn, w… fair blue-gray 57 male mascu…
# ℹ 77 more rows
# ℹ 5 more variables: homeworld <chr>, species <chr>, films <list>,
# vehicles <list>, starships <list>
Messages
message() (don’t use print() or cat())
my_filter <-function(x, ...) {if (!"wacky"%in%class(x)) {message("x is not wacky") } dplyr::filter(x, ...)}my_filter(dplyr::starwars)
x is not wacky
# A tibble: 87 × 14
name height mass hair_color skin_color eye_color birth_year sex gender
<chr> <int> <dbl> <chr> <chr> <chr> <dbl> <chr> <chr>
1 Luke Sk… 172 77 blond fair blue 19 male mascu…
2 C-3PO 167 75 <NA> gold yellow 112 none mascu…
3 R2-D2 96 32 <NA> white, bl… red 33 none mascu…
4 Darth V… 202 136 none white yellow 41.9 male mascu…
5 Leia Or… 150 49 brown light brown 19 fema… femin…
6 Owen La… 178 120 brown, gr… light blue 52 male mascu…
7 Beru Wh… 165 75 brown light blue 47 fema… femin…
8 R5-D4 97 32 <NA> white, red red NA none mascu…
9 Biggs D… 183 84 black light brown 24 male mascu…
10 Obi-Wan… 182 77 auburn, w… fair blue-gray 57 male mascu…
# ℹ 77 more rows
# ℹ 5 more variables: homeworld <chr>, species <chr>, films <list>,
# vehicles <list>, starships <list>
Catching errors
add_safe <-function(x, y) { out <-tryCatch(# named function!error =function(cnd) {# stuff to do when error occurs x },# what you are actually trying to do x + y )return(out)}add_safe(3, 5)
