## 2006-09-12

Categories: Blog post Tags: Graphical display R software

When you are producing graphics in R, the default option does not save your graphs for later review. You can change this in several ways. My comments will discuss the options for R running under Microsoft Windows. There are similar approaches that work for other systems.

First, the windows() function will create a new window in R that graphics will appear in. You don't need to use this function because the first time you use a function like plot(), the windows() function will be called with all the default options. If you do call the windows() function, you can set an argument, record, to the value of TRUE.

• windows(record=TRUE)

This will allow you to use the PgUp and PgDn keys to review the sequence of graphs. A closely related command is

• par(ask=TRUE)

which will prompt you before drawing a new graph on the screen.

Second, you can copy a bitmap version of a graph to the clipboard using the Control-C key combination. To copy a metafile version of the graph to the clipboard, use the Control-W key combination. The metafile can be scaled more easily to different sizes, but some systems interpret metafiles differently than others so the appearance of your graph may change. The bitmap is a more standard implementation, so it will not change, but be sure that the graph window is sized appropriately so your bitmap is not too small or too large.

Third, you can send the graphs directly to a printer with the win.printer() function. If you have the appropriate software, you can print to a PDF printer.

Fourth, you can produce PDF files directly by using the pdf() function. You specify the location of the file using the file option. The bmp(), jpeg(), png(), and win.metafile() functions work similarly. When you are done with producing the graphic image, use the dev.close() function to close the file and make it usable by other programs.

By default, the file that you write your graphic image to will be stored in the directory that R is stored in. On my system it is

• C:/Program Files/R/R-2.2.1

and you can change this default directory with the setwd() function. You can also specify a path in the file, but be careful. Either use the forward slash (/) to separate directories in the path, or use a double backslash (\\). A single backslash causes problems because R has special codes like \n to represent a new line.

So a  file name like

• file="C:/Data/NewProject/Scatterplot.pdf" or
• file="C:\\Data\\NewProject\\Scatterplot.pdf"

will work just fine, but

• file="C:\Data\NewProject\Scatterplot.pdf"

will not.

The pdf() functions will place multiple graphs on the same file on consecutive pages, but the other functions will overwrite the previous graph unless you specify different file names. The symbol %d embedded in a filename will create a numeric sequence (1, 2, 3, etc.). You can use one or more trailing zeros with %02d (01, 02, 03, etc.) or %03d (001, 002, 003, etc.). The default filename that R uses is  Rplot%03d with the appropriate extension.

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