Notes about the S-Plus user interface
There are two different ways to work in S-Plus:
- Using the mouse to select menu commands in the graphical user interface (GUI)
- Typing the commands as text in a window called the command line
The GUI is easy to learn and gives a quick overview of the capabilities of the S language, but many important functions are only found in the command line.
The fear factor
Most people are used to working with a mouse and menus when they use a computer at work and feel less comfortable faced with a screen showing only text and numbers. Some experience in programming with data (like writing a macro in MS Excel) helps overcome this fear and opens up an essential part of S-Plus, the ability to write additional functions.
Command line
Many tasks are actually easier to do in the command line
than in the GUI, using simple but powerful commands such as
plot(x,y) to create a scatterplot and lm(y~x) to fit
a linear regression model. Basic data manipulation, like multiplying two
columns, is straightforward from the command line, x*y, but
virtually impossible in the GUI. Using the command line is also the only way
to write additional functions, as a shorthand for frequently needed
computations or to automate complicated tasks.
What about R?
S-Plus and R are two different programs that use the S language for commands, with only slightly different dialects. They're identical 99% of the time, but the differences arise mainly in esoteric issues like calling the operating system to get some information about files or interact with other programs. The developers of R insist that S code should look the same in Windows, Unix, and Macintosh.
Although S-Plus and R are comparable in syntax and speed, there are two important differences for the user: R is free, but includes only the command line interface. Students are offered S-Plus without payment for a 12 month period, but many command line users prefer R because of its transparent and powerful architecture. Due to the growing R user community, its development is now outpacing S-Plus. See http://insightful.com and http://www.r-project.org for details.