如何將圖例高度設置爲與繪圖區域的高度相同？

Question

我已經安排了兩張圖：頂部的折線圖和下面的熱圖。

我希望熱圖圖例與熱圖的繪圖區域具有相同的高度，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，這需要進行很多試驗和錯誤。

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，並在繪製PDF時保留該比率？

與代碼重複的例子，我曾嘗試：

#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. 

我的實際數據有一些種類較多，但要點是一樣的。 Here是使用上面的代碼生成的圖像，並用我想要做的註釋進行註釋。

在此先感謝！ Maarten

Answer 1

看起來有兩套需要調整的高度：圖例按鍵的高度和圖例的整體高度。從cg grob中挑選，我提取圖例，調整高度，然後將圖例grob插回佈局。

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)