# Checks if a time series is regular

`timeSeries-isRegular.Rd`

Checks if a time series is regular.

## Usage

```
# S4 method for timeSeries
isDaily(x)
# S4 method for timeSeries
isMonthly(x)
# S4 method for timeSeries
isQuarterly(x)
# S4 method for timeSeries
isRegular(x)
# S4 method for timeSeries
frequency(x, ...)
```

## Details

What is a regular time series? If a time series is daily, monthly, or
weekly, then we speak of a regular series. This can be tested calling
the functions `isDaily`

, `isMonthly`

, `isQuarterly`

, or
in general `isRegular`

. If the series is regular then its
frequency can be determined by calling `frequency`

.

Here are the definitions of daily, monthly, and quarterly time series:

- daily
if the series has no more than one date/time stamp per day.

- monthly
if the series has no more than one date/time stamp per month.

- quarterly
if the series has no more than one date/time stamp per quarter.

A regular series is either a monthly or a quarterly series.

Note that with the above definitions a monthly series is also a daily series, a quarterly series is also a monthly series. On the other hand, a daily series is not regular!

NOT yet implemented is the case of weekly series.

## Value

The `is*`

functions return `TRUE`

or `FALSE`

depending
on whether the series fulfills the condition or not.

`frequency`

returns in general 1, for quarterly series 4,
and for monthly series 12.

## Examples

```
data(MSFT)
isRegular(MSFT) # FALSE
#> [1] FALSE
frequency(MSFT) # 1
#> [1] 1
## a monthly ts
ap <- as.timeSeries(AirPassengers)
isRegular(ap) # TRUE
#> [1] TRUE
frequency(ap) # 12
#> [1] 12
## a quarterly ts
pres <- as.timeSeries(presidents)
isRegular(pres) # TRUE
#> [1] TRUE
frequency(pres) # 4
#> [1] 4
```