Zwiększ przestrzeń między tytułem legendy a etykietami w ggplot2

Question

Próbuję zwiększyć przestrzeń między tytułem legendy a etykietami w ggplot2, ale nie miałem szczęścia stosując wszystkie możliwe rozwiązania, które mogłem znaleźć w Internecie. Jak widać w powtarzalnym przykładzie poniżej, tekst tytułu jest zbyt blisko górnej liczby. Chciałbym omijać rozwiązanie (# 6 poniżej) polegające na ręcznym dodawaniu hamulca liniowego (\n), ponieważ nie pozwala to na zmianę rozmiaru, a kompletna linia w moim przypadku jest zbyt duża.

Potrzebuję użyć colourbar. Jestem świadomy, że vjust zwykle przyjmuje wartości od 0 do 1, ale używam wartości 2 poniżej, aby łatwiej wykrywać zmiany.

library(reshape2) 
library(ggplot2) 

# Generate test data frame 
df=reshape2::melt(outer(1:4, 1:4), varnames = c("X1", "X2")) 

# Declare theme 
mytheme=theme_classic(base_size=15) + 
    theme(axis.title.x=element_blank(),axis.title.y=element_blank(), 
     axis.text.x=element_blank(),axis.text.y=element_blank(), 
     axis.ticks=element_blank()) + 
    theme(legend.position=c(0,1), legend.justification=c(0,1), 
     legend.title=element_text(size="12",face = "bold")) 

# Plot 
p=ggplot(data=df, aes_string(x="X1", y="X2")) + 
    geom_tile(aes(fill=value))+ 
    scale_fill_gradient(low="yellow",high="red",guide="colourbar",name="Titleggplot") + 
    annotate("text",x=Inf,y=Inf,label="(a)" ,hjust=1.5, vjust=1.5, size=6) + 
    mytheme 
p 

#*** Things I tried (building on the defaults above) that do not work 

# 1 - set "vjust" in theme 
mytheme=mytheme+theme(legend.title=element_text(size="12",face = "bold",vjust=2)) 
p=p+mytheme 
p 
# Result: does nothing 

# 2 - set "legend.title.align" in theme 
mytheme=mytheme+theme(legend.title.align=4) 
p=p+mytheme 
p 
# Result: adjusts horizontal position but does not change vertical position 

# 3 - increase margins around title object 
mytheme=mytheme+theme(legend.title=element_text(margin=margin(0,0,20,0),size="12",face="bold")) 
p=p+mytheme 
p 
# Result: does nothing 

# 4 - using "guide" in scale_fill_gradient 
p=ggplot(data=df, aes_string(x="X1", y="X2")) + 
    geom_tile(aes(fill=value))+ 
    scale_fill_gradient(low="yellow",high="red",guide=guide_colorbar(title="Titleggplot",title.vjust=2)) + 
    annotate("text",x=Inf,y=Inf,label="(a)" ,hjust=1.5, vjust=1.5, size=6) + 
    mytheme 
p 
# Result: does nothing 

# 5 - using "guides" as separate element 
p=p+guides(fill=guide_legend(title.vjust=2)) 
# Restult: does nothing 

# 6 - I could manually add a line break (\n) to the title 
p=ggplot(data=df, aes_string(x="X1", y="X2")) + 
    geom_tile(aes(fill=value))+ 
    scale_fill_gradient(low="yellow",high="red",guide="colourbar",name="Titleggplot\n") + 
    annotate("text",x=Inf,y=Inf,label="(a)" ,hjust=1.5, vjust=1.5, size=6) + 
    mytheme 
p 
# Result: increases the space but I can't smoothly adjust the spacing and an entire blank line is in my case too much. 

Answer 1

kopania w strukturze Grob legendy, można zastąpić oryginalny tytuł legendy z takim, który ma górny i dolny brzeg. Zobacz komentarze w kodzie poniżej.

library(reshape2) 
library(ggplot2) 


# Generate test data frame 
df=reshape2::melt(outer(1:4, 1:4), varnames = c("X1", "X2")) 

# Declare theme 
mytheme=theme_classic(base_size=15) + 
    theme(axis.title.x=element_blank(),axis.title.y=element_blank(), 
     axis.text.x=element_blank(),axis.text.y=element_blank(), 
     axis.ticks=element_blank()) + 
    theme(legend.position=c(0,1), legend.justification=c(0,1), 
     legend.title=element_text(size="12",face = "bold")) 

# Plot 
p=ggplot(data=df, aes_string(x="X1", y="X2")) + 
    geom_tile(aes(fill=value))+ 
    scale_fill_gradient(low="yellow",high="red",guide="colourbar",name="Titleggplot") + 
    annotate("text",x=Inf,y=Inf,label="(a)" ,hjust=1.5, vjust=1.5, size=6) + 
    mytheme 
p 

# Function to set upper and lower margins to legend title 

TitleMargins = function(plot, Tmargin = unit(0, "mm"), Bmargin = unit(0, "mm")) { 
library(gtable) 
library(grid) 

# Get the plot grob 
g = ggplotGrob(plot) 

# Get the legend 
index = which(g$layout$name == "guide-box") 
leg = g$grobs[[index]][[1]][[1]] 

# Get the legend title 
title = leg$grobs[[4]] 

# Set up the heights: for the two margins and the original title 
heights <- unit.c(Tmargin, unit(1, "grobheight", title), Bmargin) 

# Set up a column of three viewports 
vp <- viewport(layout = grid.layout(3, 1, 
        heights = heights), name = "vp1") 

# The middle row, where the title text will appear, is named as 'child_vp'. 
child_vp <- viewport(layout.pos.row = 2, clip = "off", name = "child_vp") 

# Put the title into a gTree containing one grob (the title) and the three viewports 
TitleText <- gTree(children = gList(title), 
        vp = vpTree(vp, vpList(child_vp))) 

# Back to the legend: Set height for row 2 of legend to new height of TitleText 
leg$heights[2] = sum(heights) 

# Add the new TitleText grob to row 2 of legend 
leg <- gtable_add_grob(leg, TitleText, 
       t = 2, l = 2, r = 5, name = "TitleText") 

# Remove the original title 
leg$grobs <- leg$grobs[-4] 
leg$layout <- leg$layout[-4, ] 

# Put the legend back into the plot 
g$grobs[[index]][[1]][[1]] = leg 

class(g) = c("TitleMargins", class(g)) 

g 

} 

# A print method for the plot 
print.TitleMargins <- function(x) { 
    grid.newpage() 
    grid.draw(x) 
} 


# Try it out 
# Set your legend title margins 
Tmargin = unit(0, "mm") 
Bmargin = unit(3, "mm") 

# Apply the function 
TitleMargins(p, Tmargin, Bmargin)