Box-Cox: calculate lambda for negative data

Machine Learning and Modeling
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Hi,

My question is how to calculate lambda for the original series y(t), if y(t) is negative or has zero's?
Because from forecast (fpp2) forecast source: R/guerrero.R says
guerrero: "Guerrero's method for selecting a Box-Cox parameter (lambda) is given for strictly positive data" and
bcloglik: Modified version of boxcox from MASS package "x must be positive".
And in feasts (fpp3) guerrero is similar feasts source: R/guerrero.R

Thus, I cannot calculate lambda for negative y(t), and use eqn(3.1), eqn(5.2) and eqn(5.3) in fpp3 (which allow for negative values of y(t) provided lambda>0), if y(t) the original series is <=0.

thanks,
Amarjit

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