How can I persuade ggplot2 geom_text to label a specified date in a time series plot?

Question

I am using ggplot2 to plot simple line charts of time series data. One difficulty I have run into is labelling specific points corresponding to x-axis values i.e. dates.

Answer 1

To add text to ggplot, use geom_text:

Method 1: Add a column of labels to your data.frame:

tmp$note <- LETTERS[1:7]

ggplot(tmp,aes(date, price, label=note)) +
  geom_line() +
  geom_text(vjust=0, colour="red")

Method 2: Add a specific label:

ggplot(tmp,aes(date, price, label=date)) +
  geom_line() +
  geom_text(data=tmp[3, ], label="Something of note", vjust=1)