User`s guide

Parametric Fitting
3-55
The fit, residuals, and numerical results are shown below.
The fit appears to be reasonable for most of the data points. However, the
residuals indicate that you should include another cycle to the fit equation.
Therefore, as a third attempt, add an additional sine and cosine term to y
2
(x)
and constrain the lower bound of c
3
to be roughly three times the value of c
1
.
The fit for two cycles.
The residuals indicate that
one more cycle might exist.
The numerical results indicate
an additional 22 month cycle.
y
3
x() y
2
x() a
3
2π
x
c
3
-----


b
3
2π
x
c
3
-----


sin+cos+=