Graphics Reference
In-Depth Information
Chapter14.Output for Presentation
Broadly speaking, visualizations of data serve two purposes: discovery and communication. In
the discovery phase, you'll create exploratory graphics, and when you do this, it's important to
be able try out different things quickly. In the communication phase, you'll present your graphics
to others. When you do that, you'll need to tweak the appearance of the graphics (which I've
written about in previous chapters), and you'll usually need to put them somewhere other than
on your computer screen. This chapter is about that last part: savingyour graphics so that they
can be presented in documents.
Outputting to PDF Vector Files
Problem
You want to create a PDF of your plot.
Solution
There are two ways to output to PDF files. One method is to open the PDF graphics device
with
pdf()
, make the plots, then close the device with
dev.off()
. This method works for most
graphics in R, including base graphics and grid-based graphics like those created by ggplot2 and
lattice:
# width and height are in inches
pdf(
"myplot.pdf"
, width
=
4
, height
=
4
)
# Make plots
plot(mtcars$wt, mtcars$mpg)
print(ggplot(mtcars, aes(x
=
wt, y
=
mpg))
+
geom_point())
dev.off()
If you make more than one plot, each one will go on a separate page in the PDF output. Notice
that we called
print()
on the
ggplot
object to make sure that it will be output even when this
code is in a script.
The
width
and
height
are in inches, so to specify the dimensions in centimeters, you must do
the conversion manually:
# 8x8 cm
pdf(
"myplot.pdf"
, width
=
8
/
2.54
, height
=
8
/
2.54
)
