Devon,
You could include an 'E' case to your rounding - I discovered it
during years of mining phone bills when my organization was
making >500k calls per month (making it well worth analysis - for
which j was a wonderful tool!) I found several phone companies whose
"rounding" algorithm was simply ceiling. That is, if a call should
have cost 8.1 cents, they would bill it at 9 cents. Reasonable
companies (e.g. AT&T) kept accuracy by using 10000*cents for the
stored call charge - but carriers who outsourced their billing to EDS
for processing got the benefit of what I dubbed "Ross Perot
rounding". (hence my suggestion of an 'E' case).
In our case, I sometimes asked for refunds around $3,000 per month
because of this rounding error - that made working on analyzing the
bill well worth while. What boggled my mind was that I had the
incentive (and the data on both sides of the calls) to dig into this
- but our few 100k calls was spit in the ocean compared to the
general public who collectively made many more calls. It is a lot
like the old chestnut of rounding down on savings account interest -
nice profit for not much work....
At 08:43 -0400 2009/03/16, Devon McCormick wrote:
>Any simple "round to integer" will do. Mine is more elaborate but
>unnecessary for this example:
>
>roundNums=: 3 : 0"1 0
>NB.* roundNums: round numbers y to precision x, e.g.
>NB. 0.1 roundNums 1.23 3.14159 2.718 -> 1.2 3.1 2.7.
>NB. Optional 2nd left argument is single letter specifying
>NB. type of rounding: Up, Down, or Banker's. Default
>NB. banker's rounding (round halves up or down depending on
>NB. parity of next (scaled) digit) tends to randomize bias.
> 1 roundNums y
>:
> RT=. 'B' NB. Default to Banker's rounding
> TO=. x NB. Precision to which to round.
> if. (2=#x)*.1=L. x do. 'TO RT'=. x end.
> scaled=. y%TO NB. For Banker's: round down if last digit even,
> select. RT
> case. 'B' do. RN=. 0.5*(0~:2|<.scaled)+.0.5~:1|scaled NB. up if odd.
> case. 'D' do. RN=. (0.5=1|scaled){0 _0.5 NB. Round halves down.
> case. 'U' do. RN=. 0.5 NB. Round halves up.
> end.
> TO*<.scaled+RN
>)
>
>
>On Sun, Mar 15, 2009 at 11:21 PM, Bill Harris <
>[email protected]> wrote:
>
>> Bill Harris <[email protected]> writes:
>>
>> > Devon McCormick <[email protected]> writes:
>>
>> >> BGYPAL3=: roundNums |:BGYPAL3
>> >
>> > Tips as to what roundNums is?
>>
>> Something like 1 & round perhaps? :-)
>>
>> Bill
>> --
>> Bill Harris http://facilitatedsystems.com/weblog/
>> Facilitated Systems Everett, WA 98208 USA
>> http://facilitatedsystems.com/ phone: +1 425 337-5541
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>
>
>
>--
>Devon McCormick, CFA
>^me^ at acm.
>org is my
>preferred e-mail
>----------------------------------------------------------------------
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