12.1 Labels

Let’s label points with the genes they represent.

Two steps:

• set the label parameter, in the ggplot aes() function, pointing to the column that contains the labels
• add the geom_text() layer, to display the labels

ggplot(data=geneexp, mapping=aes(x=WT1, y=WT2, label=GeneSymbol)) + 
  geom_point() +
  geom_text()

We can decrease or increase label size:

ggplot(data=geneexp, mapping=aes(x=WT1, y=WT2, label=GeneSymbol)) + 
  geom_point() +
  geom_text(size=3)

We can adjust the position of the labels relative to the points, so they do not overlap, with nudge_x (moves the labels horizontally / on the x axis).

ggplot(data=geneexp, mapping=aes(x=WT1, y=WT2, label=GeneSymbol)) + 
  geom_point() +
  geom_text(size=3, nudge_x=1.5)

Note that {ggrepel} package can automate the automatic organization of labels, so they do not overlap:

• Load {ggrepel} to your R session
• Change geom_text() with geom_repel_text()

ggplot(data=geneexp, mapping=aes(x=WT1, y=WT2, label=GeneSymbol)) + 
  geom_point() +
  geom_text_repel()

The warning related to the number of labels / overlaps the function will display by default. You can increase it with max.overlaps

ggplot(data=geneexp, mapping=aes(x=WT1, y=WT2, label=GeneSymbol)) + 
  geom_point() +
  geom_text_repel(max.overlaps = 100)