This example fits a function involving a sine series to
a square wave.
Fourier showed that the sum of a series of sine functions
with odd coefficients of the angle could model a square
wave if the appropriate multipliers were chosen for each
of the sine terms. A perfect fit would require an infinite
number of sine terms. In this example, we fit a sine series
with four terms to a square wave.
Here are the NLREG statements to fit this function:
Title "Fit Sine Series to Square Wave";
Function y = p0 + p1*sin(x) + p3*sin(3*x) + p5*sin(5*x) + p7*sin(7*x);
[ data goes here ]
Here is a plot generated by NLREG showing the function fitted to a
a square wave set of values.