# is.regular

##### Check Regularity of a Series

`is.regular`

is a regular function for checking whether a series of ordered observations
has an underlying regularity or is even strictly regular.

- Keywords
- ts

##### Usage

`is.regular(x, strict = FALSE)`

##### Arguments

- x
- an object (representing a series of ordered observations).
- strict
- logical. Should strict regularity be checked? See details.

##### Details

A time series can either be irregular (unequally spaced), strictly regular (equally spaced)
or have an underlying regularity, i.e., be created from a regular series by
omitting some observations. Here, the latter property is called *regular*.
Consequently, regularity follows from strict regularity but not vice versa.

`is.regular`

is a generic function for checking regularity (default) or
strict regularity. Currently, it has methods for `"ts"`

objects (which are
always strictly regular), `"zooreg"`

objects (which are at least regular),
`"zoo"`

objects (which can be either irregular, regular or even strictly regular)
and a default method. The latter coerces `x`

to `"zoo"`

before checking
its regularity.

##### Value

- A logical is returned indicating whether
`x`

is (strictly) regular.

##### See Also

##### Examples

```
## checking of a strictly regular zoo series
z <- zoo(1:10, seq(2000, 2002.25, by = 0.25), frequency = 4)
z
class(z)
frequency(z) ## extraction of frequency attribute
is.regular(z)
is.regular(z, strict = TRUE)
## by omitting observations, the series is not strictly regular
is.regular(z[-3])
is.regular(z[-3], strict = TRUE)
## checking of a plain zoo series without frequency attribute
## which is in fact regular
z <- zoo(1:10, seq(2000, 2002.25, by = 0.25))
z
class(z)
frequency(z) ## data driven computation of frequency
is.regular(z)
is.regular(z, strict = TRUE)
## by omitting observations, the series is not strictly regular
is.regular(z[-3])
is.regular(z[-3], strict = TRUE)
## checking of an irregular zoo series
z <- zoo(1:10, rnorm(10))
z
class(z)
frequency(z) ## attempt of data-driven frequency computation
is.regular(z)
is.regular(z, strict = TRUE)
```

*Documentation reproduced from package zoo, version 1.5-4, License: GPL-2*