Sine square function.
Number: 3
Names: xc, w, A, y0
Meanings: xc = phase shift, w = period, A = amplitude, y0 = offset.
Lower Bounds: w > 0.0
Upper Bounds: none
nlf_sinesqr(x,xc,w,A,y0)
FITFUNC\SINESQR.FDF
Waveform, PFW