> Anyone else have ideas on how best to do this? ~ IMHO this is so simple that I would doubt there is a "best" way to do it ;-). ~ you are the ones that know well/own the underlying data structures and logic ~ If you take a close look at: ~ http://en.wikipedia.org/wiki/Mean http://en.wikipedia.org/wiki/Standard_deviation http://en.wikipedia.org/wiki/Skewness ~ You will see that, since these are essentially summations and their exponentiations, you could derive the relationship of the new stat values based on: ~ 1) the old stat ones, 2) the count of how many have been computed so far, and 3) the new entry ~ I must run out of my place right now. If no one has done so when I come back (within 2 hours) I will digest to you/[email protected] the math, propose some pseudo code along with some basic java code on how to do that. ~ lbrtchx ~ On Sun, Jun 8, 2008 at 8:56 AM, Phil Steitz <[EMAIL PROTECTED]> wrote: > Albretch Mueller wrote: >> >> as part of >> >> http://commons.apache.org/math/ >> >> you have: >> >> >> >> http://commons.apache.org/math/apidocs/org/apache/commons/math/stat/descriptive/DescriptiveStatistics.html#addValue(double) >> >> however I don't see something like: >> >> addValue(new_val, NoV, Mean, Std_Dev, Skew) >> >> in order to get the new statistics based on the old one? >> >> It is very easy to do the Math to calculate the new Mean, Std_Dev and >> Skew, based on the old values for a certain new value >> >> Why doesn't http://commons.apache.org/math/stat/ give you that? >> > > No reason, other than that no one has suggested this. Patches are always > welcome. I am not sure what the best API would be for this enhancement, but > it would probably belong in the StatUtils class. Anyone else have ideas on > how best to do this? > > Phil > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > >
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