forecast.ts | R Documentation |
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.
## 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,
biasadj = FALSE,
find.frequency = FALSE,
allow.multiplicative.trend = FALSE,
model = NULL,
...
)
## Default S3 method:
forecast(object, ...)
## S3 method for class 'forecast'
print(x, ...)
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, |
robust |
If TRUE, the function is robust to missing values and outliers
in |
lambda |
Box-Cox transformation parameter. If |
biasadj |
Use adjusted back-transformed mean for Box-Cox transformations. If transformed data is used to produce forecasts and fitted values, a regular back transformation will result in median forecasts. If biasadj is TRUE, an adjustment will be made to produce mean forecasts and fitted values. |
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. |
model |
An object describing a time series model; e.g., one of of class
|
... |
Additional arguments affecting the forecasts produced. If
|
x |
a numeric vector or time series of class |
For example, the function forecast.Arima
makes forecasts based
on the results produced by arima
.
If model=NULL
,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).
If model
is not NULL
, forecast.ts
will apply the
model
to the object
time series, and then generate forecasts
accordingly.
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 |
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) |
Rob J Hyndman
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
.
WWWusage %>% forecast %>% plot
fit <- ets(window(WWWusage, end=60))
fc <- forecast(WWWusage, model=fit)
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