# seasonaldummy

From forecast v8.12
by Rob Hyndman

##### Seasonal dummy variables

`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.

- Keywords
- ts

##### 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.

##### Value

Numerical matrix.

##### See Also

##### 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)
# }
```

*Documentation reproduced from package forecast, version 8.12, License: GPL-3*

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