This function computes a running/rolling percentage rank.

`runPercentRank(x, n = 260, cumulative = FALSE, exact.multiplier = 0.5)`

x

Object coercible to xts or matrix.

n

Number of periods to use in the window or, if
`cumulative=TRUE`

, the number of obversations to use before the first
result is returned.

cumulative

Logical, use from-inception calculation?

exact.multiplier

The weight applied to identical values in the window. See details.

A object of percent ranks over a n-period moving window of the same
class as `x`

and `y`

or a vector (if `try.xts`

fails).

The computation for a percentage rank can vary depending on the weight given
to values in the window identical to the value being ranked. This weight can
be set using the `exact.multiplier`

argument which defaults to 0.5.

The following site(s) were used to code/document this indicator: http://en.wikipedia.org/wiki/Percentile_rank