Spencer's 15 point rule is a weighted moving average operation
for a sequence of observations equally spaced in time. The
average at time t depends on the observations at times t-7,...,t+7.
Except for boundary effects, the function will reproduce
polynomials up to degree 3.
Usage
spence.15(y)
Value
A vector with the same length as the input vector, representing
the graduated (smoothed) values.
Arguments
y
Data vector of observations at equally spaced points.
References
Spencer, J. (1904).
On the graduation of rates of sickness and mortality.
Journal of the Institute of Actuaries 38, 334-343.