03_purrr.Rmd

---
title: "Touring tidyverse"
subtitle: "purrr"
output:
  xaringan::moon_reader:
    lib_dir: libs
    nature:
      highlightStyle: github
      highlightLines: true
      countIncrementalSlides: false
---

```{r setup, include=FALSE}
options(htmltools.dir.version = FALSE)
```

background-image: url(https://raw.githubusercontent.com/tidyverse/purrr/master/man/figures/logo.png)
background-size: 100px
background-position: 90% 6%

# purrr

is a "...complete and consistent functional programming toolkit for R". It draws inspiration from multiple languages (Haskell, Scala, Javascript, `rlist` package). From vignette:

> However, the goal of purrr is not to try and simulate a purer functional programming language in R; we don’t want to implement a second-class version of Haskell in R. The goal is to give you similar expressiveness to an FP language, while allowing you to write code that looks and works like R.

---

# Why purrr

1. API responses (JSON, XML or any list-like alternatives).
2. Make lists less `r emo::ji("ghost")`.
3. Efficient abstraction over `for` loops.
4. Putting all `*apply` functions from base R into more principled framework.
5. Gateway drug to functional programming and all the goodies to go along with it (e.g., parallel programming).
6. Split-Apply-Combine paradigm.
7. List-columns.
8. Plays nicely with pipe.

---
# Initial commit of purrr

First commit: `2014-11-30 00:33` by Hadley Wickham.

---
# Current state

1. Current version - `r packageVersion("purrr")`.
1. https://github.com/tidyverse/purrr
1. Developed by __Lionel Henry__, Hadley Wickham.
1. 1000+ commits by 62 contributors.

---
background-image: url(https://raw.githubusercontent.com/tidyverse/purrr/master/man/figures/logo.png)
background-size: 100px
background-position: 90% 6%

# purrr

Covering:

1. Working with iteration in principled and safe manner.
1. ~~Functional programming.~~
1. ~~Adverbs and mappers.~~
1. ~~Utilities for working with lists.~~


```{r purrr_api, echo = FALSE}
length(getNamespaceExports("purrr"))
```

---
# Mapping

Following slides are from the Charlotte Wickham workshop that you can download here:

<a href="https://www.dropbox.com/sh/062xjv35izc2a92/AAAnC-nzToR1rPekDZipRJSLa?dl=0">bit.ly/purrr-rstudioconf</a>


---
background-image: url(https://raw.githubusercontent.com/romatik/touring_the_tidyverse/master/img/map.png)
background-size: 100%

# map

---
background-image: url(https://raw.githubusercontent.com/romatik/touring_the_tidyverse/master/img/map2.png)
background-size: 100%

# map2

---
background-image: url(https://raw.githubusercontent.com/romatik/touring_the_tidyverse/master/img/pmap.png)
background-size: 100%

# pmap


---
background-image: url(https://raw.githubusercontent.com/romatik/touring_the_tidyverse/master/img/walk.png)
background-size: 100%

# walk

---
background-image: url(https://raw.githubusercontent.com/romatik/touring_the_tidyverse/master/img/invoke_map.png)
background-size: 100%

# ~~invoke_map~~ -> rlang::exec


---
```{r, echo = FALSE}
countdown::countdown_fullscreen(minutes = 3, update_every = 30,
                     padding = "20%", margin = "5%",
                     font_size = "8em", line_height = "1.25")
````


---
# Resources

1. `purrr` tutorial by Jenny Brian - https://jennybc.github.io/purrr-tutorial/index.html
1. RStudio cheatsheet - https://github.com/rstudio/cheatsheets/blob/master/purrr.pdf
1. Parallel processing with `purrr` and `future` - https://www.jottr.org/2017/06/05/many-faced-future/ (also see https://github.com/DavisVaughan/furrr)
1. `purrr` workshop by Charlotte Wickham - https://www.dropbox.com/sh/062xjv35izc2a92/AAAnC-nzToR1rPekDZipRJSLa?dl=0
1. "Master the `tidyverse`" by Garett Grolemund - https://github.com/rstudio-education/master-the-tidyverse/.
1. `purrr::partial` example by Tyler Bradly - https://tbradley1013.github.io/2018/10/01/calculating-quantiles-for-groups-with-dplyr-summarize-and-purrr-partial/