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SD/2.3_datatransform/_demo.qmd

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+---
+title: "Lesson 8"
+format: html
+---
+
+
+```{r}
+require(tidyverse)
+library(nycflights13)
+
+flights |>
+  select(3:6) |>
+  head(3) |>
+  rename_all(~ gsub("_", "", .))
+
+
+flights |>
+  select(3:6) |>
+  head(3) |>
+  rename_with(toupper, .cols = 2:4)
+
+# 每月10号-15号，dep_delay > 100 的航班
+
+# 每月哪个出发地origin的 dep_delay总时长最长
+
+flights |>
+  group_by(month, origin) |>
+  summarize(n = n(), total_dep_delay = mean(dep_delay, na.rm = TRUE)) |>
+  slice_max(total_dep_delay)
+
+# arrange(month, origin, desc(total_dep_delay))
+
+# 每月随机抽取一天，随机抽取三个航班
+
+slice_sample(n = 1)
+
+flights |>
+  tidyr::nest(ymddf = -c(year, month, day)) |>
+  group_by(year, month) |>
+  slice_sample(n = 5) |>
+  unnest(ymddf) |>
+  group_by(year, month, day) |>
+  slice_sample(n = 3)
+
+
+flights |>
+  tidyr::nest(ymddf = -c(year, month, day)) |>
+  group_by(year, month) |>
+  slice_sample(n = 1) |>
+  mutate(
+    ymddf = purrr::map(ymddf, \(x) {
+      x |>
+        slice_sample(n = 3)
+    })
+  )
+
+# 每月 每个出发地 周末的平均dep_delay 与 工作日的平均dep_delay 差值最大的3个航班
+
+flights |>
+  mutate(date = ymd(paste(year, month, day))) |>
+  mutate(weekday = wday(date)) |>
+  mutate(isworkday = if_else(between(weekday, 2, 6), "Yes", "No")) |>
+  group_by(year, month, origin, flight, isworkday) |>
+  summarize(mean_delay = mean(dep_delay, na.rm = TRUE)) |>
+  tidyr::nest(diffdelaydf = c(isworkday, mean_delay)) |>
+  filter(
+    purrr::map(diffdelaydf, \(x) {
+      nrow(x)
+    }) >
+      1
+  ) |>
+  mutate(
+    diffdelay = purrr::map_dbl(diffdelaydf, \(x) {
+      x |>
+        arrange(isworkday) |>
+        pull(mean_delay) |>
+        diff()
+    })
+  ) |>
+  group_by(year, month, origin) |>
+  slice_max(diffdelay, n = 3)
+
+
+wday(today())
+
+weekday()
+
+
+slice_sample(n = 1)
+
+
+flights |>
+  group_by(month) |>
+  slice_sample(n = 1)
+```
+
+
+
+```{r}
+p1 <- flights |>
+  group_by(year, month) |>
+  summarize(n = n()) |>
+  ggplot(aes(month, n)) +
+  geom_point(shape = 21, size = 6, color = "black", fill = "red") +
+  geom_line()
+
+ggsave("./a.pdf")
+ggsave("./a.png")
+
+require(patchwork)
+
+p1 / p1
+```
+
+