automatically adjust R plot size in a PDF output

Question

When using the pdf() function in R for saving a plot in an external file, we can specify width and/or height to adjust the size of the plot. However, there are situations when we obtain multiple plot (say using par(mfrow=c(2,4))). In this situation, it's kind of difficult to determine what is the best width and height for the PDF file in order to have all plots displayed properly. Is there a way to let R automatically "fit the plots" in the PDF file? I searched the arguments in pdf() and tried some, but the results are not satisfactory. Thank you very much!

Answer 1

How about something using ggplot?

require(ggplot2)

# Bogus data
x <- rnorm(10000)
y <- as.factor(round(rnorm(10000, mean=10, sd=2), 0))
df <- data.frame(vals=x, factors=y)

myplot <- ggplot(data=df, aes(x=vals)) +
  geom_density() +
  facet_wrap(~ factors)

ggsave(filename="~/foo.pdf", plot=myplot, width=8, height=10, units="in")

EDIT: Should you need to print over multiple pages, see this question.