If `method=="guerrero"`

, Guerrero's (1993) method is used, where lambda
minimizes the coefficient of variation for subseries of `x`

.

BoxCox.lambda(x, method = c("guerrero", "loglik"), lower = -1, upper = 2)

x | a numeric vector or time series of class |
---|---|

method | Choose method to be used in calculating lambda. |

lower | Lower limit for possible lambda values. |

upper | Upper limit for possible lambda values. |

a number indicating the Box-Cox transformation parameter.

If `method=="loglik"`

, the value of lambda is chosen to maximize the
profile log likelihood of a linear model fitted to `x`

. For
non-seasonal data, a linear time trend is fitted while for seasonal data, a
linear time trend with seasonal dummy variables is used.

Box, G. E. P. and Cox, D. R. (1964) An analysis of
transformations. *JRSS B* **26** 211--246.

Guerrero, V.M. (1993) Time-series analysis supported by power
transformations. *Journal of Forecasting*, **12**, 37--48.

Leanne Chhay and Rob J Hyndman

lambda <- BoxCox.lambda(AirPassengers,lower=0) air.fit <- Arima(AirPassengers, order=c(0,1,1), seasonal=list(order=c(0,1,1),period=12), lambda=lambda) plot(forecast(air.fit))