Calculate a product for each period of INDEX. Essentially a rolling
application of prod over a series of non-overlapping sections.
Usage
period.prod(x, INDEX)
Arguments
x
a univariate data object
INDEX
a vector of breakpoints to calculate product on
Value
A numeric vector of products per period.
Details
Used to calculate a product per period given an arbitrary
index of sections to be calculated over. This is an optimized function
for product. There are additionally optimized versions for min, max, and
sum.