为每个站点的图例添加虚线平均

Question

我有一个 ggplot，可以为 5 个站点中的每一个绘制 3 个数据点。我根据站点对线条和点进行了颜色编码。然后，我绘制每个站点的平均值并进行颜色匹配，但将线设为虚线。我想为每个站点的图例添加一条虚线，并在图例的每条实线下添加相应的颜色。

数据

chl_no_est <- structure(list(sample_date = structure(c(1683763200, 1683763200, 
1683676800, 1683676800, 1683676800, 1689206400, 1689206400, 1689120000, 
1689120000, 1689120000, 1694649600, 1694649600, 1694563200, 1694649600, 
1694563200), tzone = "America/Los_Angeles", class = c("POSIXct", 
"POSIXt")), event = c("May 2023", "May 2023", "May 2023", "May 2023", 
"May 2023", "July 2023", "July 2023", "July 2023", "July 2023", 
"July 2023", "September 2023", "September 2023", "September 2023", 
"September 2023", "September 2023"), station_name = c("TMDL-R1", 
"TMDL-R2", "TMDL-CL", "TMDL-R3", "TMDL-R4", "TMDL-R1", "TMDL-R2", 
"TMDL-CL", "TMDL-R3", "TMDL-R4", "TMDL-R1", "TMDL-R2", "TMDL-CL", 
"TMDL-R3", "TMDL-R4"), var = c("Chlorophyll a", "Chlorophyll a", 
"Chlorophyll a", "Chlorophyll a", "Chlorophyll a", "Chlorophyll a", 
"Chlorophyll a", "Chlorophyll a", "Chlorophyll a", "Chlorophyll a", 
"Chlorophyll a", "Chlorophyll a", "Chlorophyll a", "Chlorophyll a", 
"Chlorophyll a"), result = c(8.86, 41.3, 8.01, 10.5, 112, 53.2, 
81.7, 61.9, 74.5, 103, 108, 53.3, 10.6, 27.8, 24.4), mean_var = c(56.6866666666667, 
58.7666666666667, 26.8366666666667, 37.6, 79.8, 56.6866666666667, 
58.7666666666667, 26.8366666666667, 37.6, 79.8, 56.6866666666667, 
58.7666666666667, 26.8366666666667, 37.6, 79.8)), class = c("grouped_df", 
"tbl_df", "tbl", "data.frame"), row.names = c(NA, -15L), groups = structure(list(
    station_name = c("TMDL-CL", "TMDL-R1", "TMDL-R2", "TMDL-R3", 
    "TMDL-R4"), .rows = structure(list(c(3L, 8L, 13L), c(1L, 
    6L, 11L), c(2L, 7L, 12L), c(4L, 9L, 14L), c(5L, 10L, 15L)), ptype = integer(0), class = c("vctrs_list_of", 
    "vctrs_vctr", "list"))), class = c("tbl_df", "tbl", "data.frame"
), row.names = c(NA, -5L), .drop = TRUE))



dry_season_1year_events <- data.frame(event = c("May 2023", "June 2023", "July 2023", "August 2023", "September 2023"))

代码

annotation_mean_chl <- chl_no_est %>% 
  select(event, station_name, result) %>% 
  group_by(station_name) %>% 
  mutate(avg_result = mean(result))
  


chl_no_est$event <- factor(chl_no_est$event, levels = dry_season_1year_events$event)


annotation_chl <- data.frame(
   x = c("May 2023"),
   y = c(158),
   label = c("Target Seasonal Average: 150 mg/m2")
)



ggplot() +
  geom_line(data = chl_no_est, aes(x = event, y = result, color = station_name, group = station_name), size = 0.8) +
  geom_point(data = chl_no_est, aes(x = event, y = result, color = station_name, group = station_name)) +
  theme_classic() +
  geom_hline(yintercept = c(150), linetype = "solid", color = "black", size = 0.7) +
  geom_line(data = annotation_mean_chl, aes(x=event, y=avg_result, color = station_name, group = station_name), linetype=2) +
  scale_color_viridis(discrete = TRUE, name = NULL) +
  theme(plot.title = element_text(hjust = 0.5),
        axis.title.x = element_blank(),
        legend.position = "bottom",  # Place legend under the x-axis
        legend.box = "horizontal",
        panel.grid.major.y = element_line(size=.01, color="grey60" )) +
  labs(y="Chlorophyll a (mg/m2)") +
  scale_y_continuous(limits = c(0, 200), breaks = seq(0, 200, by = 20),
                     expand = c(0,0)) +
  geom_text(data = annotation_chl, aes(x=x, y=y, label=label), nudge_x = 0.1)

没有，不确定如何继续。

Answer 1

一个快速简单的选择是使用

ggnewscale

包为虚线平均线添加第二个色标。

library(ggplot2)
library(viridis)

ggplot() +
  geom_line(data = chl_no_est, aes(x = event, y = result, color = station_name, group = station_name), size = 0.8) +
  geom_point(data = chl_no_est, aes(x = event, y = result, color = station_name, group = station_name)) +
  geom_hline(yintercept = c(150), linetype = "solid", color = "black", linewidth = 0.7) +
  geom_text(data = annotation_chl, aes(x = x, y = y, label = label), nudge_x = 0.1) +
  scale_color_viridis(
    discrete = TRUE, name = NULL,
    guide = guide_legend(order = 1)
  ) +
  ggnewscale::new_scale_color() +
  geom_line(data = annotation_mean_chl, aes(
    x = event, y = avg_result,
    color = station_name,
    group = station_name,
  ), linetype = 2) +
  scale_color_viridis(
    discrete = TRUE, name = NULL,
    guide = guide_legend(order = 2)
  ) +
  theme_classic() +
  theme(
    plot.title = element_text(hjust = 0.5),
    axis.title.x = element_blank(),
    legend.position = "bottom",
    legend.box = "vertical",
    legend.direction = "horizontal",
    panel.grid.major.y = element_line(size = .01, color = "grey60"),
    legend.margin = margin()
  ) +
  labs(y = "Chlorophyll a (mg/m2)") +
  scale_y_continuous(
    limits = c(0, 200), breaks = seq(0, 200, by = 20),
    expand = c(0, 0)
  )

更详细的方法是使用自定义键字形函数，该函数结合了两个

segmentsGrob

和

pointsGrob

来消除重复的标签。此外，这需要为

show.legend=FALSE

和第二个

geom_point

设置

geom_line

：

draw_key_cust <- function(data, params, size) {
  if (is.null(data$linetype)) {
    data$linetype <- 0
  } else {
    data$linetype[is.na(data$linetype)] <- 0
  }
  grob1 <- grid::segmentsGrob(
    0.1, 0.75, 0.9, 0.75,
    gp = grid::gpar(
      col = data$colour,
      lwd = .8 * .pt,
      lty = 1
    )
  )

  grob2 <- grid::segmentsGrob(
    0.1, 0.25, 0.9, 0.25,
    gp = grid::gpar(
      col = data$colour,
      lwd = .7 * .pt,
      lty = 2
    )
  )

  data$shape <- 19
  stroke_size <- data$stroke %||% 0.5
  stroke_size[is.na(stroke_size)] <- 0
  grob3 <- grid::pointsGrob(0.5, 0.75,
    pch = data$shape,
    gp = grid::gpar(
      col = data$colour,
      fontsize = 1.5 * .pt + stroke_size * .stroke / 2,
      lwd = stroke_size * .stroke / 2
    )
  )

  grid::gList(
    grob1,
    grob2,
    grob3
  )
}

ggplot(chl_no_est, aes(x = event, y = result, color = station_name, group = station_name)) +
  geom_line(
    linewidth = 0.8,
    key_glyph = "cust"
  ) +
  geom_point(
    show.legend = FALSE
  ) +
  geom_hline(yintercept = c(150), linetype = "solid", color = "black", linewidth = 0.7) +
  geom_text(
    data = annotation_chl, aes(x = x, y = y, label = label), nudge_x = 0.1,
    inherit.aes = FALSE
  ) +
  scale_color_viridis(
    discrete = TRUE, name = NULL,
    guide = guide_legend(order = 1)
  ) +
  geom_line(data = annotation_mean_chl, aes(
    y = avg_result
  ), linetype = 2, show.legend = FALSE) +
  theme_classic() +
  theme(
    plot.title = element_text(hjust = 0.5),
    axis.title.x = element_blank(),
    legend.position = "bottom",
    legend.box = "vertical",
    legend.direction = "horizontal",
    panel.grid.major.y = element_line(size = .01, color = "grey60"),
    legend.margin = margin()
  ) +
  labs(y = "Chlorophyll a (mg/m2)") +
  scale_y_continuous(
    limits = c(0, 200), breaks = seq(0, 200, by = 20),
    expand = c(0, 0)
  )