Question

How can I change font size and direction of axes text in ggplot2

Answer 1

You can try theme():

Library(ggplot2)
a <- data.frame(x=gl(10, 1, 10, labels=paste("long text label ", letters[1:10])), y=rnorm(10))
ggplot(a, aes(x=x, y=y)) + geom_point() + theme(text = element_text(size=20),
axis.text.x = element_text(angle=90, hjust=1)) //vjust will adjust the vertical justification of the labels