https://issues.apache.org/ooo/show_bug.cgi?id=109420
drking <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |[email protected] --- Comment #9 from drking <[email protected]> --- This page gives the US IRS system, including some maths http://www.irs.gov/publications/p946/ch04.html#en_US_2013_publink1000107554 eg: the section "Figuring the Deduction Without Using the Tables" Excel, Gnumeric, LibreOffice, ODFF and everywhere else I've looked spectacularly fail to explain the function - I think it was thrown in by Microsoft simply so they could say they had a lot of functions. It's unuseable without a proper explanation, if fractional periods are given. Certainly it looks as if when I did the wiki writeup for Ooo I didn't understand the half year convention well enough. Of course calculating to half years, half months etc is a matter of convention and definition - there are several ways it could be done - and there's nothing to say that the US system is 'right' - perhaps eg Patagonia have a better system. This is interntaional software. However I guess that Excel try to duplicate IRS policy, so that should be the target. Though what would happen if the IRS changed their policy? It does need a clearer write-up. The other issue is that calcualting between periods 0.5-2.0 for example is probably meaningless, although should be defined. Maybe the aim should be to get a current asset value for any given start/end period and take the difference. For example (I think) the asset value at endperiod 1.5 could be defined as using the half year convention (because it's got a half in it) so is calculated using a first year's depreciation based on half a year. 1.2 could be a linear interpolation between some 2 periods (which?) It certainly needs some careful thinking about. One idea would be to examine Gnumeric's code - it's quite easy to read I think, and maybe someone clever really thought about this before. Just to save re-inventing the wheel and help understand the thing. And after all this, no-one will use the function.... -- You are receiving this mail because: You are on the CC list for the issue. You are the assignee for the issue. You are watching all issue changes.
