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bcgov / ssdtools

An R package to fit and plot Species Sensitivity Distributions (SSDs)
https://bcgov.github.io/ssdtools/
Apache License 2.0
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Confirm lower bounds on shape1 and shape2 parameters in BurrIII3 #243

Open joethorley opened 2 years ago

joethorley commented 2 years ago

ie make sure not hitting 0.05 before other shape parameter hits 20

beckyfisher commented 2 weeks ago

Note that the BurrIII distribution c and k parameters are dependent on the data scaling. This is the cause of the undesirable behavior in Burrlioz, which sometimes results in a different distribution depending on the units (micrograms versus millegrams), for example. image

A solution to this is to rescale the data relative to the maximum value for this distribution by default. Suggest this is done by default for the ssd_fit_burrlioz function. How to handle this else-wise needs discussion.

beckyfisher commented 2 weeks ago

It would be good to know how to set the boundaries for the burrIII with rescaled data. This could potentially be done using a simulation study, based on the three distributions.

Note also a better solution to rescaling is to have an algorithm that determines appropriate smart boundaries given the data range.