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<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml" lang="" xml:lang="">
<head>
<title>Touring tidyverse</title>
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class: center, middle, inverse, title-slide
# Touring tidyverse
## rlang
---
background-image: url(https://raw.githubusercontent.com/r-lib/rlang/master/man/figures/rlang.png)
background-size: 100px
background-position: 90% 6%
# rlang
The rlang package provides tools to work with core language features of R and the tidyverse:
1. The tidy eval framework, which is a well-founded system for non-standard evaluation built on quasiquotation (`!!`) and quoted arguments (`enquo()`).
1. User-friendly error reporting with backtraces and chained errors (`abort()`, `trace_back()`, `with_abort()`).
1. A consistent API for working with base types. Note that overall this is a work in progress that is still in flux.
---
# Initial commit of rlang/lazyeval
First commit: `2014-08-12 21:15` by Hadley Wickham.
Current iteration of rlang is not the first attempt to introduce quasiquotation.
```r
library(lazyeval)
f = function(col1, col2, new_col_name) {
mutate_call = lazyeval::interp(~ a + b,
a = as.name(col1),
b = as.name(col2))
mtcars %>% mutate_(.dots = setNames(list(mutate_call),
new_col_name))
}
```
---
# Current state
1. Current version - 0.3.99.9003 (dev version!).
1. https://github.com/r-lib/rlang
1. Developed by __Lionel Henry__, Hadley Wickham.
1. 3200+ commits by 31 contributors.
---
# Why tidyeval
1. Programming over quoting `tidyverse` functions (e.g., `dplyr`, `ggplot2`) <sup>1</sup>.
.footnote[
[1] although it's likely you don't need it for most tasks
]
---
background-image: url(https://raw.githubusercontent.com/r-lib/rlang/master/man/figures/rlang.png)
background-size: 100px
background-position: 90% 6%
# 5 big ideas of tidyeval <sup>1</sup>
1. R code is a tree.
1. You can capture the tree by quoting.
1. Unquoting makes it easy to build trees.
1. Quoting + unquoting to write functions.
1. Quosures capture expression and environment.
.footnote[
[1] https://www.youtube.com/watch?v=nERXS3ssntw
]
---
<div class="countdown blink-colon noupdate-30" id="timer_5d036804" style="top:0;right:0;bottom:0;left:0;margin:5%;padding:20%;font-size:8em;line-height:1.25;" data-warnwhen="0">
<code class="countdown-time"><span class="countdown-digits minutes">04</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
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<code class="countdown-time"><span class="countdown-digits minutes">04</span><span class="countdown-digits colon">:</span><span class="countdown-digits seconds">00</span></code>
</div>
---
# Resources
1. `tidyeval` book - https://tidyeval.tidyverse.org/ or `tidyeval` post - https://rpubs.com/lionel-/tidyeval-introduction
1. `tidyeval` webinar - https://www.rstudio.com/resources/webinars/tidy-eval/
1. "Tidy evaluation in 5 minutes" by Hadley Wickham - https://www.youtube.com/watch?v=nERXS3ssntw
1. Metaprogramming chapters in "Advanced R" - https://adv-r.hadley.nz/meta.html
1. `tidyeval` cheatsheet - https://www.rstudio.com/resources/cheatsheets/
1. Why you might not need tidyeval - https://resources.rstudio.com/rstudio-conf-2019/working-with-names-and-expressions-in-your-tidy-eval-code and https://resources.rstudio.com/rstudio-conf-2019/lazy-evaluation
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