CODEWITHSUNDEEP
rggplot2legendfacet
AlexLee
AlexLee

Reputation: 441

ggplot: Separate legend for both a geom_vline and geom_hline

I'm trying to make a separate legend for geom_vline and geom_hline in a ggplot with facets.

Here is my code:

set.seed(1)
vec1 = rnorm(20)
set.seed(2)
vec2 = rnorm(20)
set.seed(3)
vec3 = rnorm(20)

vec  = c(vec1,vec2,vec3)
let  = rep(sample(letters[1:3],20,replace=TRUE),3)
num  = c(rep(1:20,3))
lab  = c(rep("label 1",20),rep("label 2",20),rep("label 3",20))

# Vertical lines for geom_vline
line1 = seq(1,20,5)

df   = data.frame(vector = vec, index = num, name = let, label = lab)

# Define facet order
df$label_f = factor(df$label, levels=c("label 1","label 2","label 3"))

# Dataframe for horizontal lines
hl = data.frame(label = c("label 1","label 2","label 3"), Z = c(0.5,1,-0.5))

# Factor to seperate horizontal lines for facets
hl$label_f = factor(hl$label, levels=c("label 1","label 2","label 3"))

ggplot(data=df,aes(index,vector)) + 
geom_point(aes(alpha = name, color=name)) +
geom_vline(xintercept=line1, color="blue") +
geom_hline(data = hl, aes(yintercept=Z),color="red") +
scale_alpha_manual(name="Indices",
                     labels=c("legend label 1","legend label 2","legend label 3"),
                     values=c(1,0.5,0.5)) +
scale_color_manual(name="Indices",
                     labels=c("legend label 1","legend label 2","legend label 3"),
                     values=c("black","orange","darkorange4")) +        
xlab("index") + ylab("rnorm") +  
facet_wrap(~label_f,ncol=1,scale="free_y") +
theme(legend.position="bottom")

This is the ggplot: enter image description here

I want a separate legend ("Legend 2") for the geom_hline and geom_vline with the appropriate labels and colours: enter image description here

I want the geom_hline to be horizontal and the geom_vline vertical in the legend too!

This is what it should look like: enter image description here

Thank you!

Upvotes: 2

Views: 923

Answers (2)

langtang
langtang

Reputation: 24845

One option is to use fill=name for the "color" of the geom_point(), rather than color=name.

Additionally:

  • set the pch=21
  • create a small data frame for vline_data
  • move color (say, red and blue) into the vline and hline aes()

(I additionally increased the size of the geom_points)

vline_data = data.frame(label_f = c(rep("label 1",length(line1)),rep("label 2",length(line1)),rep("label 3",length(line1))), Z = line1)

ggplot(data=df,aes(index,vector)) + 
  geom_point(aes(fill=name ), size=4,pch=21) +
  geom_vline(data = vline_data, aes(xintercept=Z, color="blue")) +
  geom_hline(data = hl, aes(yintercept=Z, color="red")) +
  scale_fill_manual(name="Indices",
                    labels=c("legend label 1","legend label 2","legend label 3"),
                    values=c("black","orange","darkorange4")
                    ) +
  scale_alpha_manual(name="Indices",
                    labels=c("legend label 1","legend label 2","legend label 3"),
                    values=c(1,0.5,0.5)) +
  scale_color_manual(name="Additional Lines",
                     labels=c("Vertical", "Horizontal"),
                     values=c("blue", "red")) +        
  xlab("index") + ylab("rnorm") +  
  facet_wrap(~label_f,ncol=1,scale="free_y") +
  theme(legend.position="bottom") + 
  guides(alpha="none")

Upvotes: 2

stefan
stefan

Reputation: 125687

Making use of ggnewscale and custom draw_key function this could be achieved like so:

  1. A separate legend for the lines could be achieved via ggnewscale::new_scale_color which will add a second color legend. Doing so requires to add a mapping to both your hline and your vline.

  2. Tricky part is that by default you will get both a vertical and a horizontal line for the legend key. To override that I added a custom key glyph function which conditions one the color of the lines. That means that if you change the colors you have to adjust the condition too.

library(ggplot2)

# Custom Key Glyph. Vertical Line if color = "blue". Horizontal Line otherwise
draw_key_cust <- function(data, params, size) {
  if (data$colour == "blue") {
    draw_key_vpath(data, params, size)
  } else {
    draw_key_path(data, params, size)
  }
}

ggplot(data=df,aes(index,vector)) + 
  geom_point(aes(alpha = name, color=name)) +
  scale_alpha_manual(name="Indices",
                     labels=c("legend label 1","legend label 2","legend label 3"),
                     values=c(1,0.5,0.5), guide = guide_legend(order = 1)) +
  scale_color_manual(name="Indices",
                     labels=c("legend label 1","legend label 2","legend label 3"),
                     values=c("black","orange","darkorange4"), guide = guide_legend(order = 1)) +
  ggnewscale::new_scale_color() +
  geom_vline(data = data.frame(xintercept = line1), aes(xintercept = xintercept, color="line1"), key_glyph = "cust") +
  geom_hline(data = hl, aes(yintercept = Z, color="line2"), key_glyph = "cust") +
  scale_color_manual(name="Legend 2",
                     labels=c(line1 ="line 1", line2 = "line 2"),
                     values=c(line1 = "blue", line2 = "red"), 
                     guide = guide_legend(order = 2)) +
  xlab("index") + ylab("rnorm") +  
  facet_wrap(~label_f,ncol=1,scale="free_y") +
  theme(legend.position="bottom")

Upvotes: 3

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