# periodicity

##### Approximate Series Periodicity

Estimate the periodicity of a time-series-like object by calculating the median time between observations in days.

- Keywords
- utilities

##### Usage

`periodicity(x, ...)`

##### Arguments

- x
time-series-like object

- …
unused

##### Details

A simple wrapper to quickly estimate the periodicity
of a given data. Returning an object of type `periodicity`

.

This calculates the median number of days between observations as a difftime object, the numerical difference, the units of measurement, and the derived scale of the data as a string.

The time index currently must be of either `Date`

or `POSIX`

class, or coercible to such.

The only list item of note is the `scale`

.
This is an estimate of the periodicity of the data
in common terms - e.g. 7 day dialy data is best
described as ‘weekly’, and would be returned as
such.

Possible `scale`

values are:

‘minute’,‘hourly’, ‘daily’,‘weekly’, ‘monthly’,‘quarterly’, and ‘yearly’.

##### Value

An object containing a list containing the `difftime`

object,
frequency, units, and suitable scale.

##### Note

This function is only a *good estimate* for
the underlying periodicity. If the series is too
short, or has *no* real periodicity, the return
values will obviously be wrong. That said, it is quite
robust and used internally within xts.

##### See Also

##### Examples

`library(xts)`

```
# NOT RUN {
zoo.ts <- zoo(rnorm(231),as.Date(13514:13744,origin="1970-01-01"))
periodicity(zoo.ts)
# }
```

*Documentation reproduced from package xts, version 0.9-7, License: GPL (>= 2)*