3_purrr.Rmd

---
title: "Touring tidyverse"
subtitle: "purrr"
author: "Misha Balyasin"
date: "2018/10/23"
output:
  xaringan::moon_reader:
    lib_dir: libs
    css: [default, robot, robot-fonts]
    nature:
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---

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

background-image: url(http://r4ds.had.co.nz/diagrams/data-science.png)
background-size: 800px

Slides, markdown and code - https://github.com/romatik/touring_the_tidyverse

---

# Plan of talks

.pull-left[
## Initial
1. Wrangle: tidyr
2. Wrangle: dplyr
3. Wrangle: lubridate, hms, blob, forcats, stringr
4. Program: purrr + glue
5. Program: tidyeval 
6. Model: rsample, tidyposterior, recipes, broom
7. Beyond tidyverse (tibbletime, tidytext, janitor)
]
--
.pull-right[
## Current
1. Wrangle: tidyr -- `r emo::ji("check")`
2. Wrangle: dplyr -- `r emo::ji("check")`
3. ~~Wrangle: lubridate, hms, blob, forcats, stringr~~
4. Program: purrr ~~and glue~~ 
5. Program: tidyeval 
6. Model: rsample, tidyposterior, recipes, broom -- `r emo::ji("construction")`
7. Beyond tidyverse (tibbletime, tidytext, janitor)

]

---
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

2. Current version - `r packageVersion("purrr")`.
3. https://github.com/tidyverse/purrr
4. Developed by __Lionel Henry__, Hadley Wickham.
5. 700+ commits by 46 contributors.

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

# purrr

Covering today:

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>


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

# map

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

# map2

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

# pmap


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

# walk

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

# invoke_map


---

# Functional programming

accumulate

accumulate_right

compose

partial

reduce

reduce_right

reduce2

reduce2_right

negate

---

# Adverbs and mappers

safely

possibly

quietly

auto_browse

lifting

as_mapper

---

# Utilities

Too many to list

---
# 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/

---
# Contacts

http://mishabalyasin.com/

Slides, markdown and code - https://github.com/romatik/touring_the_tidyverse