Put cex
inside a list. Other formatting features should also be placed in the list. See some of the examples in ?directlabels::geom_dl
library(ggplot2)
library(directlabels)
dat = data.frame(x = 1:10, y = 1:10, z = letters[1:10])
ggplot(dat, aes(x, y)) +
geom_point() +
geom_dl(aes(label = z), method = list(cex = 2, rot = -45, hjust = -.5))
EDIT
The method too is placed in the list:
ggplot(dat, aes(x, y)) +
geom_point() +
geom_dl(aes(label = z), method = list("smart.grid", cex = 2))