The forecast function allows you to produce future predictions of a time series from fitted models. If the response variable has been transformed in the model formula, the transformation will be automatically back-transformed (and bias adjusted if bias_adjust is TRUE). More details about transformations in the fable framework can be found in vignette("transformations", package = "fable").

forecast(object, ...)

# S3 method for mdl_df
forecast(object, new_data = NULL, h = NULL, point_forecast = "mean", ...)

Arguments

object

The time series model used to produce the forecasts

...

Additional arguments for forecast model methods.

new_data

A tsibble containing future information used to forecast.

h

The forecast horison (can be used instead of new_data for regular time series with no exogenous regressors).

point_forecast

Which point forecast measure should be returned in the resulting fable (possible values include: "mean", "median").

bias_adjust

Deprecated. Please use point_forecast to specify the desired point forecast method.

Value

A fable containing the following columns:

  • .model: The name of the model used to obtain the forecast. Taken from the column names of models in the provided mable.

  • The point forecast, which by default is the mean. The name of this column will be the same as the dependent variable in the model(s).

  • .distribution. A column of objects of class fcdist, representing the statistical distribution of the forecast in the given time period.

  • All columns in new_data, excluding those whose names conflict with the above.

Details

The forecasts returned contain both point forecasts and their distribution. A specific forecast interval can be extracted from the distribution using the hilo() function, and multiple intervals can be obtained using report(). These intervals are stored in a single column using the hilo class, to extract the numerical upper and lower bounds you can use tidyr::unnest().

Examples

if (requireNamespace("fable", quietly = TRUE)) { library(fable) library(tsibble) library(tsibbledata) library(dplyr) library(tidyr) # Forecasting with an ETS(M,Ad,A) model to Australian beer production beer_fc <- aus_production %>% model(ets = ETS(log(Beer) ~ error("M") + trend("Ad") + season("A"))) %>% forecast(h = "3 years") # Compute 80% and 95% forecast intervals beer_fc %>% hilo(level = c(80, 95)) beer_fc %>% autoplot(aus_production) # Forecasting with a seasonal naive and linear model to the monthly # "Food retailing" turnover for each Australian state/territory. library(dplyr) aus_retail %>% filter(Industry == "Food retailing") %>% model( snaive = SNAIVE(Turnover), ets = TSLM(log(Turnover) ~ trend() + season()), ) %>% forecast(h = "2 years 6 months") %>% autoplot(filter(aus_retail, Month >= yearmonth("2000 Jan")), level = 90) # Forecast GDP with a dynamic regression model on log(GDP) using population and # an automatically chosen ARIMA error structure. Assume that population is fixed # in the future. aus_economy <- global_economy %>% filter(Country == "Australia") fit <- aus_economy %>% model(lm = ARIMA(log(GDP) ~ Population)) future_aus <- new_data(aus_economy, n = 10) %>% mutate(Population = last(aus_economy$Population)) fit %>% forecast(new_data = future_aus) %>% autoplot(aus_economy) }
#> Warning: 1 error encountered for ets #> [1] .data contains implicit gaps in time. You should check your data and convert implicit gaps into explicit missing values using `tsibble::fill_gaps()` if required.
#> Error: `mutate()` argument `ets` errored. #> `ets` is `(function (object, ...) ...`. #> non-numeric argument to mathematical function