[Jprogramming] Everyone giving dollars to random others

[Raul Miller]

Why do you think that?

Or were you referring to Xiao-Yong Jin's narrative?

Thanks,

-- 
Raul

On Mon, Jul 10, 2017 at 5:17 PM, Devon McCormick <devonmcc at gmail.com> wrote:
> So, you start with $10,000 (=100*$100) but end up with $2,025 (=45*$45),
> how?
>
> On Mon, Jul 10, 2017 at 3:59 PM, Raul Miller <rauldmiller at gmail.com> wrote:
>
>> I don't really understand what you mean by "mean expectations" - could
>> you describe the intent there?
>>
>> That said, here's how far I've gotten in implementing this concept:
>>
>>    tick=: (0 >. <:) + i.@# +/@:(=/)~ +/@:* ?@# #
>>    (mean,stddev)"1 tick^:(i.10)]100#100
>> 100        0
>> 100 0.932034
>> 100  1.41421
>> 100  1.91749
>> 100  2.07437
>> 100  2.34844
>> 100  2.48633
>> 100  2.71546
>> 100  2.97803
>> 100  3.26289
>>
>> (Also, for animation in J, there's actually a lot of options...
>> basically though you set up a paint event which calls into your
>> rendering code and then trigger updates from systimer.)
>>
>> Thanks,
>>
>> --
>> Raul
>>
>> On Mon, Jul 10, 2017 at 3:43 PM, Xiao-Yong Jin <jinxiaoyong at gmail.com>
>> wrote:
>> > I thought this is a good lunch break exercise.
>> >
>> > http://www.decisionsciencenews.com/2017/06/19/counterintuitive-
>> problem-everyone-room-keeps-giving-dollars-random-others-
>> youll-never-guess-happens-next/
>> >
>> > Quote: “Imagine a room full of 100 people with 100 dollars each. With
>> every tick of the clock, every person with money gives a dollar to one
>> randomly chosen other person. After some time progresses, how will the
>> money be distributed?”
>> >
>> > And I came up with this simulation.  (45 people with 45 dollars each,
>> same as on the webpage.)
>> >
>> >  /:~@(-&1`]@.(=&0)"0 (#/.~@] + ~.@]{[)`(~.@])`[} >&0 # (?@#~@#@]`]`[}
>> ]I.@:=i.@#)^:_@?@#~@#)^:5000 #~45
>> >
>> > And I really like to see the mean expectations and the standard
>> deviation of the mean, I ended up doing this.  (Make sure the J sentence is
>> one long line if you want to try it out.)
>> >
>> >     ((],.[:(+/%#*<:@#)&.:*: -"1)+/%#)}.(/:~@(-&1`]@.(=&0)"0 (#/.~@] +
>> ~.@]{[)`(~.@])`[} >&0 # (?@#~@#@]`]`[} ]I.@:=i.@#)^:_@?@#~@#)^:10000)^:(<65)
>> #~45
>> > 0.984375 0.124984
>> >  2.01562 0.170335
>> >   3.0625 0.180765
>> >  4.15625 0.230616
>> >  5.21875 0.248476
>> >   6.1875 0.306894
>> >  7.35938 0.332862
>> >  8.64062 0.362809
>> >  9.84375 0.380723
>> >  10.9688 0.383805
>> >   12.125 0.407944
>> >  13.6406 0.423964
>> >  15.0625 0.457453
>> >  16.5312 0.462893
>> >  18.1875 0.480717
>> >  19.7031 0.464877
>> >  21.1562 0.475709
>> >  22.7031 0.483702
>> >  24.4062 0.516935
>> >  26.4062   0.5768
>> >  28.1094 0.604266
>> >  29.8281 0.617838
>> >   31.875  0.61942
>> >  33.9375 0.603345
>> >  35.7812 0.642211
>> >  37.9844 0.647987
>> >  40.6562 0.731321
>> >       43 0.739342
>> >  45.3906 0.723616
>> >  48.0469   0.7613
>> >  51.6094 0.823639
>> >  54.7656 0.873934
>> >  57.1406 0.815544
>> >       60 0.866598
>> >  63.8594 0.898319
>> >    68.75 0.918018
>> >  73.5781  1.00736
>> >  78.3281  1.08128
>> >  84.9688  1.25534
>> >  93.4688  1.29731
>> >  104.578  1.73274
>> >  114.922  2.07574
>> >  131.938   2.7357
>> >  159.359  4.40899
>> >  204.766  7.24239
>> >
>> > So, how do I make a fancy animation (like the one in the webpage I
>> linked in the beginning of this message) with J?
>> > ----------------------------------------------------------------------
>> > For information about J forums see http://www.jsoftware.com/forums.htm
>> ----------------------------------------------------------------------
>> For information about J forums see http://www.jsoftware.com/forums.htm
>>
>
>
>
> --
>
> Devon McCormick, CFA
>
> Quantitative Consultant
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm