gnuplot has built-in a respectable collection of special functions and mathematical operators that allow us to perform significant calculations and massaging of data before plotting. A complete survey of gnuplot's math brain is beyond the scope of this book; interested readers should start with Chapter 13 of the official reference manual distributed with the program and available at http://gnuplot.info/documentation.html.
Here, we shall merely give an example of one very useful technique for plotting functions that have different definitions over different domains; this technique works equally well for functions that are continuous or discontinuous over the entire plotting domain. The example will demonstrate several of gnuplot's mathematical facilities that have not been covered up to now. Following figure is a plot of two functions, a simple sine wave that turns into a decaying sine wave when we cross x = 0:
