At 3:17 PM -0500 5/19/06, Richard Lynch wrote:
On Fri, May 19, 2006 1:27 pm, Sébastien Guay wrote:
I searched the archives but did not found anything.
It seem that the round function behavior has changed in php 4.4.x (I
don't
have 4.4.1 handy for testing).
In 4.3.11, the output of round("23.005",2) is 23.01 which is
mathematically
correct.
In 4.4.2, the output is 23 which is not correct. The output of
round("23.0051",2) is correct though (23.01).
Is there a workaround/patch for this?
The correctness of rounding kinda depends on which
mathematical/historical model one subscribes to.
There is at least one statistician's model of 'round' wherein a
trailing '5' goes 'up' for preceding even numbers and 'down' for
preceding odd numbers, to provide more symmetry in statistical
analysis of rounding.
Or, at least, that's how I recall it.
Your recall is correct.
The reasoning is that for a trailing 1-4, you
round down; for 6-9, you round up; and for 0 you
don't do anything, but for five it becomes a
statistical problem as to which way you round.
If you always round up, then the bias is up. If
you always round down (which I believe php does),
then the bias is down.
However, if you use the statistician's model (up
for even and down for odd whole numbers), then
rounding errors are reduced as compared to other
methods, but they are not eliminated.
tedd
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