# forecast {forecast}

### Description

`forecast`

is a generic function for forecasting from time series or time series models. The function invokes particular *methods* which depend on the class of the first argument.

For example, the function `forecast.Arima`

makes forecasts based on the results produced by `arima`

.

The function `forecast.ts`

makes forecasts using `ets`

models (if the data are non-seasonal or the seasonal period is 12 or less) or `stlf`

(if the seasonal period is 13 or more).

### Usage

forecast(object,...) ## S3 method for class 'ts': forecast((object, h = ifelse(frequency(object) > 1, 2 * frequency(object), 10) , level=c(80,95), fan=FALSE, robust=FALSE, lambda=NULL, find.frequency=FALSE, allow.multiplicative.trend=FALSE, ...))

### Arguments

- object
- a time series or time series model for which forecasts are required
- h
- Number of periods for forecasting
- level
- Confidence level for prediction intervals.
- fan
- If TRUE,
`level`

is set to`seq(51,99,by=3)`

. This is suitable for fan plots. - robust
- If TRUE, the function is robust to missing values and outliers in
`object`

. This argument is only valid when`object`

is of class`ts`

. - lambda
- Box-Cox transformation parameter.
- find.frequency
- If TRUE, the function determines the appropriate period, if the data is of unknown period.
- allow.multiplicative.trend
- If TRUE, then ETS models with multiplicative trends are allowed. Otherwise, only additive or no trend ETS models are permitted.
- ...
- Additional arguments affecting the forecasts produced.
`forecast.ts`

passes these to`forecast.ets`

or`stlf`

depending on the frequency of the time series.

### Values

An object of class "`forecast`

".

The function `summary`

is used to obtain and print a summary of the results, while the function `plot`

produces a plot of the forecasts and prediction intervals.

The generic accessors functions `fitted.values`

and `residuals`

extract various useful features of the value returned by `forecast$model`

.

An object of class `"forecast"`

is a list usually containing at least the following elements:

- model
- A list containing information about the fitted model
- method
- The name of the forecasting method as a character string
- mean
- Point forecasts as a time series
- lower
- Lower limits for prediction intervals
- upper
- Upper limits for prediction intervals
- level
- The confidence values associated with the prediction intervals
- x
- The original time series (either
`object`

itself or the time series used to create the model stored as`object`

). - residuals
- Residuals from the fitted model. For models with additive errors, the residuals will be x minus the fitted values.
- fitted
- Fitted values (one-step forecasts)

### See Also

Other functions which return objects of class `"forecast"`

are `forecast.ets`

, `forecast.Arima`

, `forecast.HoltWinters`

, `forecast.StructTS`

, `meanf`

, `rwf`

, `splinef`

, `thetaf`

, `croston`

, `ses`

, `holt`

, `hw`

.

Documentation reproduced from package forecast, version 7.1. License: GPL (>= 2)