---
title: "Data Transform"
format:
  dwsd-revealjs:
    logo: _extensions/drwater/dwsd/inst/ucaslogo.png
---

```{r}
#| include: false
#| cache: false
lang <- "cn"
require(tidyverse)
require(learnr)
knitr::opts_chunk$set(echo = TRUE)
```

```{r}
#| echo: false
source("../../coding/_common.R")
library(nycflights13)
library(tidyverse)
```


## `tidyverse`风格数据分析总体流程

![](../../image/data-science/transform.png) 


## [dplyr cheatsheet](../../image/cheatsheet/data-transformation.pdf)


```{r}
#| echo: false
dwfun::ggsavep("../../image/cheatsheet/data-transformation.svg", loadit = TRUE)
```



## 查看数据

```{r}
flights
```


## 选择列

```{r}
#| results: false

flights |>
  select(year, month, day)
```

## 选择列

```{r}
#| results: false

flights |>
  select(year:day)
```


## 选择列

```{r}
flights |>
  select(3:5)
```

## 选择列

```{r}
flights |>
  select(!year:day)
```

## 选择列

```{r}
flights |>
  select(-(year:day))
```

## 选择列

```{r}
flights |>
  select(where(is.character))
```

## 选择列

```{r}
flights |>
  select(!where(is.character)) |>
  select(contains("_"))
```

## 选择列

```{r}
flights |>
  select(tail_num = tailnum)
```

## 选择列

```{r}
flights |>
  select(air_time, everything())
```


## 重命名

```{r}
flights |>
  rename(tail_num = tailnum)
```

## 重命名

```{r}
flights |>
  rename(年份 = 1) |>
  rename(月份 = 2)
```

## 重命名

```{r}
flights |> select(1:4) |> head(n = 3)
# 重命名
flights |> select(1:4) |> head(n = 3) |> rename_all(~ c("c1", "c2", "c3", "c4"))
```

## 重命名

```{r}
flights |> select(1:4) |> head(n = 3)
# 重命名
flights |> select(1:4) |> head(n = 3) |> rename_all(toupper)
```


## 重命名

```{r}
flights |> select(1:4) |> head(n = 3)
# 重命名
flights |>
  select(1:4) |>
  head(n = 3) |>
  rename_all(~ paste0(toupper(.), "_NEW"))
```


## 练习

将含有下划线的列名中的下划线去掉。


```{r}
flights |> select(1:4) |> head(n = 3)
```


## 练习

将`airqualitydf`中列名的单位信息去除（前5列）。


```{r}
airqualitydf <- readxl::read_xlsx("../../data/airquality.xlsx", sheet = 2)
airqualitydf |> select(1:5)
```



## `filter`

```{r}
flights |>
  filter(dep_delay > 120)
```

## filter 练习

Flights that departed on January 1.

```{r}
#| echo: false
flights |>
  filter(month == 1 & day == 1)
```

## filter 练习


Select flights that departed in January or February

```{r}
#| echo: false
flights |>
  filter(month %in% c(1, 2))
```

## filter 练习

```{r}
jan1 <- flights |>
  filter(month == 1 & day == 1)
```

## filter

```{r}
#| error: true
#| eval: false

flights |>
  filter(month = 1)
```

## filter

```{r}
flights |>
  filter(month == 1 | 2)
```

## 排序

```{r}
flights |>
  arrange(year, month, day, dep_time)
```

## 排序

```{r}
flights |>
  arrange(desc(dep_delay))
```

## slice

```{r}
flights |> head(n = 5)
flights |> slice(1:5)
```

## slice

```{r}
flights |>
  slice_max(dep_delay, n = 5)
```

## slice

```{r}
flights |>
  slice_min(dep_delay, prop = 0.005)
```

## 排序练习

根据`origin`、`dest`、`air_time`倒序排序。

```{r}
#| echo: false
flights |>
  arrange(origin, dest, desc(air_time)) |>
  select(origin, dest, air_time, everything())
```


## 去重

```{r}
# Remove duplicate rows, if any
flights |>
  distinct()
```

## 去重

```{r}
# Find all unique origin and destination pairs
flights |>
  distinct(origin, dest)
```

## 去重

```{r}
flights |>
  distinct(origin, dest, .keep_all = TRUE)
```



## 欢迎讨论！{.center}

```{r}
#| results: 'asis'
rmdify::slideend(
  wechat = FALSE,
  type = "public",
  tel = FALSE,
  thislink = "../"
)
```

