[Jprogramming] Everyone giving dollars to random others

[Raul Miller]

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