Formulas for ODF

01Sep07

An Antic Disposition: The Formula for Failure

So what is ODF doing about formulas? We’re continuing to work on them. Rather than rush, we’re doing careful, methodical work. We’re documenting the functions in great detail. Where we have the choice between the common naive formula for a function and one that is numerically stable, we’re documenting the stable function. For the NETWORKDAYS function, we created an optional extra parameter, so a user can pass in a flag that tells what their weekend conventions are. We have a professor of statistics reviewing our statistics functions for completeness and accuracy. We’re verifying our assumptions about financial functions by referring to core specifications from groups like the ISDA and the NASD. We’re creating a huge number of test cases and checking them with Excel and other applications.

That’s encouraging. Excel has well known flaws in its statistical functions–doing OLS, for example, can give you misleading coefficients–and the OpenOffice/ODF guys are actually having a stats professor check their work. Awesome.

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