forecast: accuracy – R documentation

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accuracy

Accuracy measures for a forecast model

Description

Returns range of summary measures of the forecast accuracy. If x is provided, the function measures test set forecast accuracy based on x-f. If x is not provided, the function only produces training set accuracy measures of the forecasts based on f["x"]-fitted(f). All measures are defined and discussed in Hyndman and Koehler (2006).

Usage

accuracy(object, ...)

## Default S3 method:
accuracy(object, x, test = NULL, d = NULL, D = NULL, f = NULL, ...)

Arguments

`object`	An object of class “`forecast`”, or a numerical vector containing forecasts. It will also work with `Arima`, `ets` and `lm` objects if `x` is omitted – in which case training set accuracy measures are returned.
`...`	Additional arguments depending on the specific method.
`x`	An optional numerical vector containing actual values of the same length as object, or a time series overlapping with the times of `f`.
`test`	Indicator of which elements of `x` and `f` to test. If `test` is `NULL`, all elements are used. Otherwise test is a numeric vector containing the indices of the elements to use in the test.
`d`	An integer indicating the number of lag-1 differences to be used for the denominator in MASE calculation. Default value is 1 for non-seasonal series and 0 for seasonal series.
`D`	An integer indicating the number of seasonal differences to be used for the denominator in MASE calculation. Default value is 0 for non-seasonal series and 1 for seasonal series.
`f`	Deprecated. Please use 'object' instead.

Details

The measures calculated are:

ME: Mean Error
RMSE: Root Mean Squared Error
MAE: Mean Absolute Error
MPE: Mean Percentage Error
MAPE: Mean Absolute Percentage Error
MASE: Mean Absolute Scaled Error
ACF1: Autocorrelation of errors at lag 1.

By default, the MASE calculation is scaled using MAE of training set naive forecasts for non-seasonal time series, training set seasonal naive forecasts for seasonal time series and training set mean forecasts for non-time series data. If f is a numerical vector rather than a forecast object, the MASE will not be returned as the training data will not be available.

See Hyndman and Koehler (2006) and Hyndman and Athanasopoulos (2014, Section 2.5) for further details.

Value

Matrix giving forecast accuracy measures.

Author(s)

Rob J Hyndman

References

Hyndman, R.J. and Koehler, A.B. (2006) "Another look at measures of forecast accuracy". International Journal of Forecasting, 22(4), 679-688. Hyndman, R.J. and Athanasopoulos, G. (2018) "Forecasting: principles and practice", 2nd ed., OTexts, Melbourne, Australia. Section 3.4 "Evaluating forecast accuracy". https://otexts.com/fpp2/accuracy.html.

Examples

fit1 <- rwf(EuStockMarkets[1:200, 1], h = 100)
fit2 <- meanf(EuStockMarkets[1:200, 1], h = 100)
accuracy(fit1)
accuracy(fit2)
accuracy(fit1, EuStockMarkets[201:300, 1])
accuracy(fit2, EuStockMarkets[201:300, 1])
plot(fit1)
lines(EuStockMarkets[1:300, 1])

forecast

Forecasting Functions for Time Series and Linear Models

v8.14

GPL-3

Authors

Rob Hyndman [aut, cre, cph] (<https://orcid.org/0000-0002-2140-5352>), George Athanasopoulos [aut], Christoph Bergmeir [aut] (<https://orcid.org/0000-0002-3665-9021>), Gabriel Caceres [aut], Leanne Chhay [aut], Mitchell O'Hara-Wild [aut] (<https://orcid.org/0000-0001-6729-7695>), Fotios Petropoulos [aut] (<https://orcid.org/0000-0003-3039-4955>), Slava Razbash [aut], Earo Wang [aut], Farah Yasmeen [aut] (<https://orcid.org/0000-0002-1479-5401>), R Core Team [ctb, cph], Ross Ihaka [ctb, cph], Daniel Reid [ctb], David Shaub [ctb], Yuan Tang [ctb] (<https://orcid.org/0000-0001-5243-233X>), Zhenyu Zhou [ctb]

Initial release