Graphical Parameters

You can customize many features of your graphs (fonts, colors, axes, titles) through graphic options.

One way is to specify these options in through the par( ) function. If you set parameter values here, the changes will be in effect for the rest of the session or until you change them again. The format is par(optionname=value, optionname=value, ...)

# Set a graphical parameter using par()

par()              # view current settings
opar <- par()      # make a copy of current settings
par(col.lab="red") # red x and y labels
hist(mtcars$mpg)   # create a plot with these new settings
par(opar)          # restore original settings

A second way to specify graphical parameters is by providing the optionname=value pairs directly to a high level plotting function. In this case, the options are only in effect for that specific graph.

# Set a graphical parameter within the plotting function
hist(mtcars$mpg, col.lab="red")

See the help for a specific high level plotting function (e.g. plot, hist, boxplot) to determine which graphical parameters can be set this way.

The remainder of this section describes some of the more important graphical parameters that you can set.

Text and Symbol Size

The following options can be used to control text and symbol size in graphs.

option description
cex number indicating the amount by which plotting text and symbols should be scaled relative to the default. 1=default, 1.5 is 50% larger, 0.5 is 50% smaller, etc.
cex.axis magnification of axis annotation relative to cex
cex.lab magnification of x and y labels relative to cex
cex.main magnification of titles relative to cex
cex.sub magnification of subtitles relative to cex

Plotting Symbols

Use the pch= option to specify symbols to use when plotting points. For symbols 21 through 25, specify border color (col=) and fill color (bg=).

plotting symbols

 

Lines

You can change lines using the following options. This is particularly useful for reference lines, axes, and fit lines.

option description
lty line type. see the chart below.
lwd line width relative to the default (default=1). 2 is twice as wide.

line types

 

Colors

Options that specify colors include the following.

option description
col Default plotting color. Some functions (e.g. lines) accept a vector of values that are recycled.
col.axis color for axis annotation
col.lab color for x and y labels
col.main color for titles
col.sub color for subtitles
fg plot foreground color (axes, boxes - also sets col= to same)
bg plot background color

You can specify colors in R by index, name, hexadecimal, or RGB.
For example col=1, col="white", and col="#FFFFFF" are equivalent.

The following chart was produced with code developed by Earl F. Glynn. See his Color Chart for all the details you would ever need about using colors in R.

R color chart

You can also create a vector of n contiguous colors using the functions rainbow(n), heat.colors(n), terrain.colors(n), topo.colors(n), and cm.colors(n).

colors() returns all available color names.

Fonts

You can easily set font size and style, but font family is a bit more complicated.

option description
font Integer specifying font to use for text.
1=plain, 2=bold, 3=italic, 4=bold italic, 5=symbol
font.axis font for axis annotation
font.lab font for x and y labels
font.main font for titles
font.sub font for subtitles
ps font point size (roughly 1/72 inch)
text size=ps*cex
family font family for drawing text. Standard values are "serif", "sans", "mono", "symbol". Mapping is device dependent.

In windows, mono is mapped to "TT Courier New", serif is mapped to"TT Times New Roman", sans is mapped to "TT Arial", mono is mapped to "TT Courier New", and symbol is mapped to "TT Symbol" (TT=True Type). You can add your own mappings.

# Type family examples - creating new mappings
plot(1:10,1:10,type="n")
windowsFonts(
  A=windowsFont("Arial Black"),
  B=windowsFont("Bookman Old Style"),
  C=windowsFont("Comic Sans MS"),
  D=windowsFont("Symbol")
)
text(3,3,"Hello World Default")
text(4,4,family="A","Hello World from Arial Black")
text(5,5,family="B","Hello World from Bookman Old Style")
text(6,6,family="C","Hello World from Comic Sans MS")
text(7,7,family="D", "Hello World from Symbol")

font example click to view

Margins and Graph Size

You can control the margin size using the following parameters.

option description
mar numerical vector indicating margin size c(bottom, left, top, right) in lines. default = c(5, 4, 4, 2) + 0.1
mai numerical vector indicating margin size c(bottom, left, top, right) in inches
pin plot dimensions (width, height) in inches

For complete information on margins, see Earl F. Glynn's margin tutorial.

Going Further

See help(par) for more information on graphical parameters. The customization of plotting axes and text annotations are covered next section.