如何將圖例高度設置為與繪圖區域的高度相同？

Question

我已經安排了兩個圖：頂部的折線圖和下面的熱圖。

我希望熱圖圖例的高度與熱圖的繪圖區域相同，即與y軸的長度相同。 我知道我可以使用theme(legend.key.height = unit(...))更改圖例的高度和大小，但在找到適當的設置之前，這將需要許多試驗和錯誤。

有沒有辦法指定圖例的高度，使其與熱圖的繪圖區域的高度完全相同，並在繪制為pdf時保留該比率？

我可以嘗試使用代碼重現的示例：

#Create some test data
pp <- function (n, r = 4) {
  x <- seq(1:100)
  df <- expand.grid(x = x, y = 1:10)
  df$z <- df$x*df$y
  df
}
testD <- pp(20)
#Define groups
colbreaks <- seq(min(testD[ , 3]), max(testD[ , 3] + 1), length = 5)
library(Hmisc)
testD$group <- cut2(testD[ , 3], cuts = c(colbreaks))
detach(package:Hmisc, unload = TRUE)

#Create data for the top plot
testD_agg <- aggregate(.~ x, data=testD[ , c(1, 3)], FUN = sum)

#Bottom plot (heatmap)
library(ggplot2)
library(gtable)

p <- ggplot(testD, aes(x = x, y = y)) +
  geom_tile(aes(fill = group)) +
  scale_fill_manual(values = c("red", "orange", "yellow", "lightgreen")) +
  coord_cartesian(xlim = c(0, 100), ylim = c(0.5, 10.5)) +

  theme_bw() +
  theme(legend.position = "right",
        legend.key = element_blank(),
        legend.text = element_text(colour = "black", size = 12),
        legend.title = element_blank(),
        axis.text.x = element_text(size = 12, angle = 45, vjust = +0.5),
        axis.text.y = element_text(size = 12),
        axis.title = element_text(size = 14),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(),
        plot.margin = unit(c(0, 0, 0, 0), "line"))

#Top plot (line)
p2 <- ggplot(testD_agg, aes(x = x, y = z)) +
  geom_line() +
  xlab(NULL) +
  coord_cartesian(xlim = c(0, 100), ylim = c(0, max(testD_agg$z))) +

  theme_bw() +
  theme(legend.position = "none",
        legend.key = element_blank(),
        legend.text = element_text(colour = "black", size = 12),
        legend.title = element_text(size = 12, face = "plain"),
        axis.text.x = element_blank(),
        axis.text.y = element_text(size = 12),
        axis.title = element_text(size = 14),
        axis.ticks.x = element_blank(),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(),
        plot.margin = unit(c(0.5, 0.5, 0, 0), "line"))

#Create gtables
gp <- ggplotGrob(p) 
gp2 <- ggplotGrob(p2)

#Add space to the right of the top plot with width equal to the legend of the bottomplot 
legend.width <- gp$widths[7:8] #obtain the width of the legend in pff2
gp2 <- gtable_add_cols(gp2, legend.width, 4) #add a colum to pff with with legend.with
#combine the plots
cg <- rbind(gp2, gp, size = "last")
#set the ratio of the plots
panels <- cg$layout$t[grep("panel", cg$layout$name)]
cg$heights[panels] <- unit(c(2,3), "null")
#remove white spacing between plots
cg <- gtable_add_rows(cg, unit(0, "npc"), pos = nrow(gp))

pdf("test.pdf", width = 8, height = 7)
print(grid.draw(cg))
dev.off()

#The following did not help solve my problem but I think I got close
old.height <- cg$grobs[[16]]$heights[2]
#It seems the height of the legend is given in "mm", change to "npc"?
gp$grobs[[8]]$grobs[[1]]$heights <- c(rep(unit(0, "npc"), 3), rep(unit(1/4, "npc"), 4), rep(unit(0, "mm"),1))
#this does allow for adjustment of the heights but not the exact control I need.

我的實際數據有更多類別，但要點是相同的。 這是使用上面的代碼生成的圖像，並注釋了我想要做的事情。

提前致謝！ 馬騰

Answer 1

似乎有兩組高度需要調整：圖例鍵的高度和圖例的整體高度。 從你的cg grob中提取，我提取圖例，調整高度，然后將圖例grob插回到布局中。

leg = gtable_filter(cg, "guide-box")

library(grid)

# Legend keys
leg[[1]][[1]][[1]][[1]]$heights = unit.c(rep(unit(0, "mm"), 3),
                                         rep(unit(1/4, "npc"), 4),
                                         unit(0, "mm"))

# Legend
leg[[1]][[1]]$heights[[3]] = sum(rep(unit(0, "mm"), 3),
                                 rep(unit(1/4, "npc"), 4),
                                 unit(0, "mm"))

# grid.draw(leg)  # Check that heights are correct

cg.new = gtable_add_grob(cg, leg, t = 17, l = 8)

grid.newpage()
grid.draw(cg.new)