Add a legend when one already exists

Question

[Loïs]

Hello,

I have the following R code which allows me to make a heatmap, as follows :

library(ggplot2)
library(ggtext)

test_data <- read.csv("/home/veillat/Bureau/heatmap.csv")
test_data$Species <- factor(test_data$Species, levels = unique(test_data$Species))
test_data$Conditions <- factor(test_data$Conditions, levels = unique(test_data$Conditions))

# Définition des couleurs en fonction de la colonne "Conservation"
color_mapping <- c("wet" = "blue", "dry" = "darkgoldenrod1", "Hand collected" = "darkgreen")

# Ajouter une colonne avec les étiquettes colorées pour chaque espèce
test_data$Species_Label <- paste0("<i><span style='color:", color_mapping[test_data$Conservation], "'>", test_data$Species, "</span></i>")

# Réorganiser l'ordre des labels de l'axe X
test_data$Species_Label <- factor(test_data$Species_Label, levels = unique(test_data$Species_Label))

# Création du graphique
ggplot(test_data, aes(x = Species_Label, y = Conditions, fill = Detection)) +
  geom_raster() +
  geom_tile(color = "black", size = 0.3) +
  scale_fill_manual(values = c("green", "red")) +
  theme(axis.text.x = element_text(angle = 90, vjust = 0.5, hjust = 1, face = "italic"),
        strip.text.y = element_blank()) +
  ggtitle("") +
  facet_grid(rows = vars(Conditions), cols = vars(Bulk), scales = "free", space = "free_y") +
  theme(axis.text.x = element_markdown()) +
  guides(x = guide_axis(n.dodge = 1)) +
  xlab("Species")+
  labs(fill = "Detection and Collection type")

I'd have to add information about the colours of the labels on the X axis to the existing legend. So in my case a blue square corresponding to condition 1, a dark yellow square for condition 2 and a dark green square for condition 3.

How can I do this?

Thanks in advance

Answer 1

[iraun]

You could use Legend from ComplexHeatmap package.

lgd = Legend(labels = names(color_mapping), title = "Legend title", labels_gp = gpar(fontsize = 10), legend_gp = gpar(fill = color_mapping))
draw(lgd)

I haven't tested the code with your specific example, but I hope it serves you as guide :).