Saving your graphs

Of course, you will need to save many of the graphs that you create. The simplest method is to click inside the graph and then copy as a metafile or copy as a bitmap. You can then save your graph in a Word document or within a PowerPoint presentation. However, you may wish to save your graphs as JPEGS, PDFs, or in other formats.

Now we shall create a PDF of a graph (a histogram that we will create using the hist() command, which you will come across later in this book). First we get ready to create a PDF (in R, we refer to this procedure as opening the PDF device driver) using the command pdf(), and then we plot. Finally, we complete the job (closing the device driver) using the command dev.off().

You may wish to save your plot to a particular directory or folder. To do so, navigate to File | Change Dir in R and select the directory or folder that you wish to use as your R working directory. For example, I selected a directory called BOOK, which is located within the following filepath on my computer:

C:\Users\David\Documents\BOOK

To confirm that this folder is now my current working folder, I entered the following command:

getwd()

The output obtained is as follows:

[1] "C:/Users/David/Documents/BOOK"

R has confirmed that its working folder is the one that I wanted. Note that R uses forward slashes for filepaths. Now, we create a vector of data and create our histogram as follows:

  y <- c(7, 18, 5, 13, 6, 17, 7, 18, 28, 7,17,28)

 pdf("My_Histogram.pdf")
 hist(y, col = "darkgreen")
 dev.off()

A PDF of your histogram should be saved in your R working directory. It is called My_Histogram.pdf and it looks like the following:

The graphing options available in R include postscript(), pdf(), bitmap(), and jpeg(). For a complete list of options, navigate to Help | Search help and enter the word devices. The list you need is labelled List of graphical devices.

For example, to create a postscript plot of the histogram, you can use the following syntax:

postscript(file="myplot.ps")
hist(y, col = "darkgreen")
dev.off()

To create and save a JPEG image from the current graph, use the dev.copy()command:

dev.copy(device=jpeg,file="picture.jpg")
dev.off()

Your image is saved in the R working directory.

You can save and recall a plot that is currently displayed on your screen. If you have a plot on your screen, then try the following commands:

x = recordPlot()
x

You can delete your plot but get it back again later in your session using the following command:

replayPlot(x)