weibull halflife depends on data length

facebookexperimental / Robyn

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weibull halflife depends on data length #255

Closed slavakx closed 2 years ago

slavakx commented 2 years ago

Hi,

trying to understand how you calculate weibull adstock, I figured out that scaleTrans depends on the time units. So having a fixed scale and shape params, halflife will be different based on time units. Is this a correct behavior? Example: time units of 20 (halflife ~6.5 weeks) and 100 has a halflife of 18 weeks.

gufengzhou commented 2 years ago

Hi, yes it's expected. Scale is the relative position