21  基础

library(tidyverse)
library(ggh4x)
library(patchwork)

make_block <- function(age, n, inc_range, mort_range){

  tibble(
    AGEGR = age,
    Metric = rep(c("Incidence", "Mortality"), each = n),
    Country = rep(paste0("C", 1:n), times = 2),
    est = c(
      runif(n, inc_range[1], inc_range[2]),
      runif(n, mort_range[1], mort_range[2])
    )
  )
}

df <- bind_rows(
  make_block("0-<6m",   3,  c(60,120), c(5,15)),
  make_block("6-<12m",  7,  c(30,80),  c(3,10)),
  make_block("12-<24m", 12, c(10,40),  c(1,5))
) %>%
  group_by(AGEGR, Metric) %>%
  mutate(
    lci = est * runif(n(), 0.8, 0.9),
    uci = est * runif(n(), 1.1, 1.2)
  ) %>%
  ungroup()

df

base_plot <- ggplot(df, aes(Country, est)) +
  geom_pointrange(aes(ymin = lci, ymax = uci)) +
  theme_bw() +
  labs(x = NULL, y = "Estimate") +
  theme(axis.text.x = element_text(angle = 45, hjust = 1))

p_wrap <- base_plot +
  facet_wrap(~ AGEGR + Metric, scales = "free_y", ncol = 2) +
  ggtitle("facet_wrap: flattened display")

p_grid <- base_plot +
  facet_grid(Metric ~ AGEGR, scales = "free_x", space = "free") +
  ggtitle("facet_grid: structured layout")

p_grid2 <- base_plot +
  facet_grid2(
    Metric ~ AGEGR,
    scales = "free",
    independent = "y"
  ) +
  ggtitle("facet_grid2: flexible axes per panel")

p_wrap

p_grid

p_grid2

21.1 facet_grid

params <- crossing(
  scales = c("fixed", "free_x", "free_y", "free"),
  space  = c("fixed", "free")
)

pwalk(params, \(scales, space){

  print(
    base_plot +
      facet_grid(Metric ~ AGEGR,
                 scales = scales,
                 space = space) +
      ggtitle(paste0("scales=", scales, " | space=", space))
  )

})

21.2 facet_wrap

params_wrap <- crossing(
  scales = c("fixed", "free_x", "free_y", "free"),
  ncol   = c(2, 3)
)

pwalk(params_wrap, \(scales, ncol){

  print(
    base_plot +
      facet_wrap(~ Metric + AGEGR,
                 scales = scales,
                 ncol = ncol) +
      ggtitle(paste0("[wrap] scales=", scales, " | ncol=", ncol))
  )

})

21.3 facet_grid2

params_grid2 <- bind_rows(
  # 1. 基础组合：scales 为 free 时，independent 可以匹配
  tibble(scales = "free_x", space = "fixed", independent = "x"),
  tibble(scales = "free_y", space = "fixed", independent = "y"),
  
  # 2. 只有 space = "fixed" 时，independent 才能设为 "all"
  tibble(scales = "free", space = "fixed", independent = "all"),
  
  # 3. 只有 independent = "none" 时，space 才能设为 "free"
  # 注意：space 必须对应 scales 的 free 维度
  tibble(scales = "free_x", space = "free_x", independent = "none"),
  tibble(scales = "free_y", space = "free_y", independent = "none"),
  tibble(scales = "free",   space = "free",   independent = "none")
)

# 执行循环
pwalk(params_grid2, \(scales, space, independent){
  
  p <- base_plot +
    facet_grid2(
      Metric ~ AGEGR,
      scales = scales,
      space = space,
      independent = independent
    ) +
    ggtitle(paste0(
      "grid2 | s=", scales,
      " | sp=", space, 
      " | ind=", independent
    ))
  
  print(p)
})