---
title: 课后作业8
author: 姓名
format: html
---

# 数据

下载airquality.xlsx，并读取数据。

```{r}
#| message: false
#| warning: false
# 下载至临时文件
if (FALSE) {
  tmpxlsxpath <- file.path(tempdir(), "airquality.xlsx")
  download.file("https://drwater.rcees.ac.cn/git/course/RWEP/raw/branch/PUB/data/airquality.xlsx",
    destfile = tmpxlsxpath)
  airqualitydf <- readxl::read_xlsx(tmpxlsxpath, sheet = 2)
  metadf <- readxl::read_xlsx(tmpxlsxpath, sheet = 1)
  saveRDS(airqualitydf, "./airqualitydf.RDS")
  saveRDS(metadf, "./metadf.RDS")
}
airqualitydf <- readRDS("./airqualitydf.RDS")
metadf <- readRDS("./metadf.RDS")
```

# 描述统计

根据`airqualitydf.xlsx`，按采样点统计白天（8:00-20:00）与夜晚（20:00-8:00）中空气质量指数（AQI）中位数，按城市统计低于所有采样点AQI30%分位值的采样点占比，列出上述占比最高的10个城市（不考虑采样点数低于5个的城市）。

```{r}
#| message: false
#| warning: false
require(tidyverse)
airqualitydf |>
  select(datetime, site, AQI) |>
  filter(!is.na(AQI)) |>
  group_by(site) |>
  summarize(AQI.median = median(AQI, na.rm = TRUE)) |>
  left_join(metadf |> select(site, city = Area)) |>
  group_by(city) |>
  filter(n() > 5) |>
  summarize(p = sum(AQI.median < quantile(airqualitydf$AQI, probs = 0.5, na.rm = TRUE)) / n()) |>
  top_n(10, p)


airqualitydf |>
  select(datetime, site, AQI) |>
  filter(!is.na(AQI)) |>
  group_by(site) |>
  summarize(AQI.median = median(AQI, na.rm = TRUE))

airqualitydf |>
  select(datetime, site, AQI) |>
  filter(!is.na(AQI)) |>
  left_join(metadf |> select(site, city = Area)) |>
  group_by(city) |>
  filter(length(unique(site)) >= 5) |>
  summarize(p = sum(AQI < quantile(airqualitydf$AQI, probs = 0.2,
    na.rm = TRUE)) / n()) |>
  slice_max(p, n = 10) |>
knitr::kable()


```


# 统计检验

按照不同城市分组，统计白天与夜晚AQI中位数是否具有显著差异。

```{r}
#| message: false
#| warning: false

if (FALSE) {
  require(infer)
  require(tidyverse)
  testdf <- airqualitydf |>
    select(datetime, site, AQI) |>
    filter(!is.na(AQI)) |>
    left_join(metadf |> select(site, city = Area)) |>
    group_by(city) |>
    filter(length(unique(site)) >= 5) |>
    mutate(dayornight = factor(ifelse(between(hour(datetime), 8, 20), "day", "night"),
      levels = c("day", "night"))
    ) |>
    group_by(city) |>
    nest(citydf = -city) |>
    mutate(median_diff = purrr::map_dbl(citydf, ~
      .x |>
        specify(AQI ~ dayornight) |>
        calculate(stat = "diff in medians", order = c("day", "night")) |>
        pull(stat)
    )) |>
    ungroup() |>
    #  slice_sample(n = 12) |>
    mutate(null_dist = purrr::map(citydf, ~
      .x |>
        specify(AQI ~ dayornight) |>
        hypothesize(null = "independence") |>
        generate(reps = 1000, type = "permute") |>
        calculate(stat = "diff in medians", order = c("day", "night"))
    )) |>
    mutate(p_value = purrr::map2_dbl(null_dist, median_diff, 
      ~  get_p_value(.x, obs_stat = .y, direction = "both") |>
        pull(p_value)
    )) |>
    mutate(sigdiff = ifelse(p_value < 0.01, "显著差异", "无显著差异")) |>
    mutate(fig = purrr::pmap(list(null_dist, median_diff, city, sigdiff),
      ~ visualize(..1) +
      shade_p_value(obs_stat = ..2, direction = "both") +
      ggtitle(paste0(..3, "：", ..4)) +
      theme_sci(2, 2)
    )) |>
    arrange(p_value)
  saveRDS(testdf, "./testdf.RDS")
}

if (FALSE) {

lang <- "cn"
require(dwfun)
require(rmdify)
require(drwateR)
dwfun::init()
rmdify::rmd_init()

testdf <- readRDS("./testdf.RDS")
require(tidyverse)
testdf |>
  select(city, median_diff, p_value, sigdiff) |>
  knitr::kable()
testdf |>
  mutate(grp = (row_number() - 1)%/% 12) |>
  group_by(grp) |>
  nest(grpdf = -grp) |>
  ungroup() |>
#  slice(1) |>
  mutate(gp = purrr::map(grpdf,
    ~(.x |>
      pull(fig)) |>
      patchwork::wrap_plots(ncol = 3) +
      dwfun::theme_sci(5, 7))) |>
  pull(gp)


}

```