croston {forecast} | R Documentation |
Returns forecasts and other information for Croston's forecasts applied to x.
croston(x, h=10, alpha)
x |
a numeric vector or time series |
h |
Number of periods for forecasting. |
alpha |
Value of alpha. If missing, it is estimated. |
Based on Croston's (1972) method for intermittent demand
forecasting, also described in Shenstone and Hyndman (2005).
Croston's method involves using simple exponential smoothing (SES) on
the non-zero elements of the time series and a separate application
of SES to the times between non-zero elements of the time series. The
smoothing parameters of the two applications of SES are assumed to be
equal and are denoted by alpha
. If alpha
is omitted, it
is estimated by averaging the two alpha values selected for each
series by the HoltWinters
function.
Note that prediction intervals are not computed as Croston's method has no underlying stochastic model.
An object of class "forecast"
is a list 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 |
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. That is x minus fitted values. |
fitted |
Fitted values (one-step forecasts) |
The function summary
is used to obtain and print a summary of
the results, while the function plot
produces a plot of the
forecasts.
The generic accessor functions fitted.values
and
residuals
extract useful features of the value returned by
croston
and associated functions.
Rob J Hyndman
Croston, J. (1972) "Forecasting and stock control for intermittent demands", Operational Research Quarterly, 23(3), 289-303.
Shenstone, L., and Hyndman, R.J. (2005) "Stochastic models underlying Croston's method for intermittent demand forecasting". Journal of Forecasting, 24, 389-402.
ses
.
x <- rpois(20,lambda=.3) fcast <- croston(x) plot(fcast)