Paul M Foster wrote: > On Mon, Jan 11, 2010 at 04:56:03PM -0500, tedd wrote: > >> --Rick: >> >> The above described rounding algorithm introduces more bias than >> simply using PHP's round() function, which always rounds down. IMO, >> modifying rounding is not worth the effort. >> >> The "best" rounding algorithm is to look at the last digit and do this: >> >> 0 -- no rounding needed. >> 1-4 round down. >> 6-9 round up. >> >> In the case of 5, then look to the number that precedes it -- if it >> is even, then round up and if it is odd, then round down -- or vise >> versa, it doesn't make any difference as long as you are consistent. >> >> Here are some examples: >> >> 122.4 <-- round down (122) >> 122.6 <-- round up (123) >> 122.5 <-- round up (123) >> >> 123.4 <-- round down (123) >> 123.6 <-- round up (124) >> 123.5 <-- round down (123) >> >> There are people who claim that there's no difference, or are at odds >> with this method, but they simply have not investigated the problem >> sufficiently to see the bias that rounding up/down causes. However, >> that difference is very insignificant and can only be seen after tens >> of thousands iterations. PHP's rounding function is quite sufficient. > > This is called (among other things) "banker's rounding". But PHP's > round() function won't do banker's rounding, as far as I know. > > Paul > floor( $val + 0.5 ); -- PHP General Mailing List (http://www.php.net/) To unsubscribe, visit: http://www.php.net/unsub.php
