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From "Mark R. Diggory" <>
Subject Re: [math] Apples or Oranges
Date Mon, 16 Jun 2003 20:15:29 GMT
Al Chou wrote:

>--- "Mark R. Diggory" <> wrote:
>>Andreou Andreas wrote:
>>>Mark, I would go for the latter approach (the one on the p.s.) cause 
>>>it doesn't seem that complex to me...
>>>Why not add a CachableUnivariateImpl class
>>>that extends UnivariateImpl
>>>and also keeps track in a cache the results of the getters (getMean, 
>>>getKurtosis, e.t.c.).
>>>In this way, whenever a new value is added, the cache will be cleared, 
>>>and on calling the getters, each correspending statistic will be
>>>If no new values have been added, this new subclass will just return 
>>>the cached results... 
>>Yes, I think this is a novel idea to explore in the future, its 
>>difficult to draw the lines on what to store in it because at this time, 
>>we are now calculating the mean/variance in addValue with Al's new 
>>2-pass algorithm, while the more complex kurt and skew calculations are 
>>in the getter methods. But, I like the idea of it. I'm working on 2-pass 
>>style algorithms for skew and kurt now. Which may unfortunately require 
>>more calculation to occur in addValue than I want to see happening.
>Before I say something more substantive about the original question, I just
>want to shoot out a "huh?" about "my" "2-pass" algorithm.  I think of what I
>submitted over the weekend as a 1-pass storage-less/updating algorithm.
>I did mention that the corrected 2-pass algorithm had not yet been implemented
>in StoreUnivariateImpl.
I'm pulling my hair out, yes, your right, you implemented Wests 
algorithm, not the Two-Pass. My bad referencing.


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