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+---
+title: "Data Transform"
+subtitle: 《区域水环境污染数据分析实践》<br>Data analysis practice of regional water environment pollution
+author: 苏命、王为东<br>中国科学院大学资源与环境学院<br>中国科学院生态环境研究中心
+date: today
+lang: zh
+format:
+  revealjs:
+    theme: dark
+    slide-number: true
+    chalkboard:
+      buttons: true
+    preview-links: auto
+    lang: zh
+    toc: true
+    toc-depth: 1
+    toc-title: 大纲
+    logo: ./_extensions/inst/img/ucaslogo.png
+    css: ./_extensions/inst/css/revealjs.css
+    pointer:
+      key: "p"
+      color: "#32cd32"
+      pointerSize: 18
+revealjs-plugins:
+  - pointer
+filters:
+  - d2
+---
+
+```{r}
+#| echo: false
+knitr::opts_chunk$set(echo = TRUE)
+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 rmdify::slideend(wechat = FALSE, type = "public", tel = FALSE, thislink = "https://drc.drwater.net/course/public/RWEP/PUB/SD/")`
+