# seasonaldummy: Seasonal dummy variables

## Description

`seasonaldummy`

returns a matrix of dummy variables suitable for use in
`Arima`

, `auto.arima`

or `tslm`

. The
last season is omitted and used as the control.

## Usage

seasonaldummy(x, h = NULL)seasonaldummyf(x, h)

## Arguments

x

Seasonal time series: a `ts`

or a `msts`

object

h

Number of periods ahead to forecast (optional)

## Details

`seasonaldummyf`

is deprecated, instead use the `h`

argument in
`seasonaldummy`

.

The number of dummy variables is determined from the time series
characteristics of `x`

. When `h`

is missing, the length of
`x`

also determines the number of rows for the matrix returned by
`seasonaldummy`

. the value of `h`

determines the number of rows
for the matrix returned by `seasonaldummy`

, typically used for
forecasting. The values within `x`

are not used.

## Examples

# NOT RUN {
plot(ldeaths)
# Using seasonal dummy variables
month <- seasonaldummy(ldeaths)
deaths.lm <- tslm(ldeaths ~ month)
tsdisplay(residuals(deaths.lm))
ldeaths.fcast <- forecast(deaths.lm,
data.frame(month=I(seasonaldummy(ldeaths,36))))
plot(ldeaths.fcast)
# A simpler approach to seasonal dummy variables
deaths.lm <- tslm(ldeaths ~ season)
ldeaths.fcast <- forecast(deaths.lm, h=36)
plot(ldeaths.fcast)
# }