---
layout: default
title: Data transformation
output: bookdown::html_chapter
---

Copy from dplyr vignettes.

## Filter

### Missing values

* Why `NA == NA` is not `TRUE`
* Why default is `na.rm = FALSE`.

## Mutate

## Arrange

## Select

## Grouped summaries

Overview of different data types and useful summary functions for working with them. Strings and dates covered in more detail in future chapters.   Anything complicated can be put off until data structures chapter.

### Logical

When used with numeric functions, `TRUE` is converted to 1 and `FALSE` to 0. This makes `sum()` and `mean()` particularly useful: `sum(x)` gives the number of `TRUE`s in `x`, and `mean(x)` gives the proportion.

### Numeric (integer and double)

### Strings (and factors)

### Date/times

## Grouped mutate
