Currently the uncertainty in the loss ratios can only be modelled with a lognormal distribution. This uncertainty can also be modelled with a beta distribution, which can also be defined by two parameters: a mean and a standard deviation or an alpha and beta values.
This feature affects the loss ratio sampler and the creation of the loss ratio exceedance matrices.
Openquake now should not assume the distribution of loss ratio as lognormal, but to read in the vulnerability file which type of distribution is being considered.
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Open Issues:
- Which calculators does this change affect?
- Are there any changes to output formats?
- What are the changes to input files?
- If there are changes, we need a set of demo input files which can exercise this functionality. We also need demo files to write a QA test.
- We can probably utilize scipy.stats.beta [1] for this bug. Where do the alpha and beta values come from?
[1] - http://docs.scipy.org/doc/scipy/reference/generated/scipy.stats.beta.html
More details needed.
- Which calculators does this change affect?
- Are there any changes to output formats?
- Is there test data available (input + expected results)?
- Are the formulae for this new type of calculation somewhere? If so, where?