forecast (version 2.14)

forecast.lm: Forecasting using lm objects

Description

Returns forecasts obtained from linear models with explanatory variables specified by newdata.

Usage

## S3 method for class 'lm':
forecast(object, newdata, level=c(80,95), fan=FALSE, ...)

Arguments

object
An object of class "lm". Usually the result of a call to lm.
newdata
An optional data frame or matrix in which to look for variables with which to predict.
level
Confidence level for prediction intervals.
fan
If TRUE, level is set to seq(50,99,by=1). This is suitable for fan plots.
...
Other arguments passed to predict.lm().

Value

  • 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 accessor functions fitted.values and residuals extract useful features of the value returned by forecast.lm. An object of class "forecast" is a list containing at least the following elements:
  • modelA list containing information about the fitted model
  • methodThe name of the forecasting method as a character string
  • meanPoint forecasts as a time series
  • lowerLower limits for prediction intervals
  • upperUpper limits for prediction intervals
  • levelThe confidence values associated with the prediction intervals
  • xThe original time series (either object itself or the time series used to create the model stored as object).
  • residualsResiduals from the fitted model. That is x minus fitted values.
  • fittedFitted values (one-step forecasts)

Details

forecast.lm produces predicted values, obtained by evaluating the regression function in newdata. It is largely a wrapper to predict.lm and returns the output in the form of a forecast object. If the original data are time series, the function will make the forecasts time series with the appropriate parameters.

See Also

predict.lm, lm.

Examples

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