Yes, the don't-do-that advice is controversial. Computing mean value and standard deviation is elegant E +/ % # ES E , E&.:*:&(- E) ES +/? 100 100$2 50.02 5.12636
--- Den fre 24/9/10 skrev Kip Murray <k...@math.uh.edu>: Fra: Kip Murray <k...@math.uh.edu> Emne: Re: [Jprogramming] Classification problem Til: programming@jsoftware.com Dato: fredag 24. september 2010 17.08 About "Don't do that!" modern statistics texts recommend the five-number summary Minimum Q1 M Q3 Maximum as a reasonably complete description of center and spread. M Q1 Q3 are the median and quartiles, see David S. Moore and George P. McCabe, Introduction to the Practice of Statistics, p. 42, for a description of how to calculate. (Find the median, then find the median of observations below the median and the median of observations above the median. J exercise: find the five number summary of a list.) Kip Murray On 9/24/2010 1:37 AM, Bo Jacoby wrote: > First comes relevance, then correctness, performance, and elegance in some > order. Not every problem is put right. For example. Question: from a long > list of numbers, how to compute the 15th, 50th and 85th percentile? Answer: > Don't do that! Compute the mean value and the standard deviation instead. > Venlig hilsen, Bo > > > --- Den tors 23/9/10 skrev Roger Hui<rhui...@shaw.ca>: > > Fra: Roger Hui<rhui...@shaw.ca> > Emne: Re: [Jprogramming] Classification problem > Til: "Programming forum"<programming@jsoftware.com> > Dato: torsdag 23. september 2010 16.48 > > At first I was going to respond to R.E. Boss with a > cute and annoying reply, something like "first comes > elegance, then elegance, then elegance". But I think > now I agree with him, "first comes correctness, then > performance, then elegance", rather than "first comes > elegance and correctness". A counterexample to the > latter is a model for dyadic index-of for vectors. > An elegant and correct model is: > > ix=: #...@[ - (+/)@(+./\)@(=/) > > But due to abysmal performance this is pretty useless > in practice. > > I guess it depends on what you mean by "first comes". > If you were implementing dyadic index-of you _would_ > first writing something like the above, but almost > immediately you write something else. > > > > ----- Original Message ----- > From: Robert Raschke<rtrli...@googlemail.com> > Date: Thursday, September 23, 2010 6:57 > Subject: Re: [Jprogramming] Classification problem > To: Programming forum<programming@jsoftware.com> > >> I disagree, first comes elegance and correctness, and these tend >> to go hand >> in hand if you are concentrating on elegance. I quite strongly >> believe a >> human reader is way more important than any machine. >> >> Robby >> >> On Thu, Sep 23, 2010 at 2:24 PM, R.E. Boss >> <r.e.b...@planet.nl> wrote: >> >>> I agree. First comes correctness, then performance, then elegance. >>> >>> >>> R.E. Boss >>> >>> >>>> -----Oorspronkelijk bericht----- >>>> Van: programming-boun...@jsoftware.com [mailto:programming- >>>> boun...@jsoftware.com] Namens Brian Schott >>>> Verzonden: donderdag 23 september 2010 14:41 >>>> Aan: Programming forum >>>> Onderwerp: Re: [Jprogramming] Classification problem >>>> >>>> I agree that this solution is elegant, but for a large data >> set I >>>> assume that Raul's idea of prepending and then dropping 3 elements >>>> would be more efficient. Don't you, too? >>>> >>>> (<@}./.~ *) _1 0 1,data >>>> >>>> On Thu, Sep 23, 2010 at 8:26 AM, R.E. Boss >> <r.e.b...@planet.nl> wrote: >>>>> One of the more elegant solutions is >>>>> >>>>> ((/:&(*</. ])) *) data >>>>> +---------------+---+-----+ >>>>> |_3 _1 _10 _2 _4|0 0|1 1 6| >>>>> +---------------+---+-----+ >>>>> >>>>> >>>>> R.E. Boss >>>>> >>>>> >>>>>> -----Oorspronkelijk bericht----- >>>>>> Van: programming-boun...@jsoftware.com >> [mailto:programming- >>>>>> boun...@jsoftware.com] Namens Marshall Lochbaum >>>>>> Verzonden: woensdag 22 september 2010 23:57 >>>>>> Aan: Programming forum >>>>>> Onderwerp: Re: [Jprogramming] Classification problem >>>>>> >>>>>> It looks to me like the most terse way is >>>>>> ((</. /: ~...@[)~ f) data >>>>>> >>>>>> Although this computes the nub twice, unlike some earlier >> solutions.> > >> >>>>>> Marshall >>>>>> >>>>>> ________________________________________ >>>>>> From: programming-boun...@jsoftware.com [programming- >>>>>> boun...@jsoftware.com] On Behalf Of Raul Miller [ >>> rauldmil...@gmail.com] >>>>>> Sent: Wednesday, September 22, 2010 3:29 PM >>>>>> To: Programming forum >>>>>> Subject: Re: [Jprogramming] Classification problem >>>>>> >>>>>> Note, if * is the universe of interesting >>>>>> functions (if it does not need to be generic) then >>>>>> I would be tempted to use a variation on Dan's >>>>>> second suggestion: >>>>>> >>>>>> (<@}./.~ *) _1 0 1,data >>>>>> >>>>>> Note that this also preserves the relative >>>>>> ordering of the data items. > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm > > > ---------------------------------------------------------------------- > For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
