Add a legend for a geom_text layer to explain labels

Question

Consider the following example where a scatter is made and only the "significant" point are colored and labelled.

genes <- read.table("https://gist.githubusercontent.com/stephenturner/806e31fce55a8b7175af/raw/1a507c4c3f9f1baaa3a69187223ff3d3050628d4/results.txt", header = TRUE)
genes$Significant <- ifelse(genes$padj < 0.05, "FDR < 0.05", "Not Sig")
ggplot(genes, aes(x = log2FoldChange, y = -log10(pvalue))) +
  geom_point(aes(color = Significant)) +
  scale_color_manual(values = c("red", "grey")) +
  theme_bw(base_size = 12) + theme(legend.position = "bottom") +
  geom_text_repel(
    data = subset(genes, padj < 0.05),
    aes(label = Gene),
    size = 5,
    box.padding = unit(0.35, "lines"),
    point.padding = unit(0.3, "lines")
  )

It yields the following plot

Now imagine that the labels are actually acronyms and that they have a real full-length name (e.g., "DOK6" is the acronym for "Duo Ocarino Kayne 6"). Would it be possible to add a legend to the plot where the keys are the labels used on the plot, and the entries are the full-length name of the labels ?

Perhaps this approach? https://stackoverflow.com/questions/12318120/adding-table-within-the-plotting-region-of-a-ggplot-in-r — Jon Spring, Apr 30 '22 at 16:59

score 1 · Accepted Answer · answered Apr 30 '22 at 23:00

First, I added Gene2 for another legend which only shows significant Gene.\

Next, Gene2 was added on the aes as a fill. (Only color would affect the color of points on geom_point).\

Finally, scale_fill_discrete was added for the second legend. All you need to do is just annotate the full-length name column at Full names here.

genes$Gene2 <-ifelse(genes$padj<0.05, genes$Gene, NA)
ggplot(genes, aes(x = log2FoldChange, y = -log10(pvalue),
                  fill=Gene2)) +
  geom_point(aes(color = Significant)) +
  scale_color_manual(values = c("red", "grey")) +
  theme_bw(base_size = 12) + theme(legend.position = "bottom") +
  geom_text_repel(
    data = subset(genes, padj < 0.05),
    aes(label = Gene),
    size = 5,
    box.padding = unit(0.35, "lines"),
    point.padding = unit(0.3, "lines")
  ) +
  scale_fill_discrete(labels=paste0(genes$Gene,': ',' Full names here'),
                      name='Significant genes') +
  theme(legend.position = 'right')

Output

Add a legend for a geom_text layer to explain labels

1 Answers1