# Ehrenfest Urn Model

Model was written in NetLogo 5.0.4
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;;;;;;;;;;;;;;;;;;;;;; ;; setup procedures ;; ;;;;;;;;;;;;;;;;;;;;;; globals [ prob ratio ;; ratio between number of balls in urn A and total number of balls urnA ;; number of balls in urn A sum-ratio sum-ratio-square mean-ratio mean-ratio-square var ] ;; sets up the patches and creates turtles to setup clear-all ask patches [ set pcolor gray + 3 ] crt 1 [ set color black set shape "dot" set pen-size 3 setxy 0 0 set heading 0 pd forward 50 die ] init-vars setup-turtles reset-ticks end to init-vars set ratio (ratio-two-urns / (1 + ratio-two-urns)) set urnA (number-of-particles * ratio) set sum-ratio 0 set sum-ratio-square 0 end ;; determines the number of turtles and their color to setup-turtles create-turtles urnA [ set size 2 set shape "dot" set ycor (random-float 50) set xcor (- (random-float 24)) - 1 set color blue ] create-turtles (number-of-particles - urnA) [ set size 2 set shape "dot" set ycor (random-float 50) set xcor (random-float 24) + 1 set color red ] end ;;;;;;;;;;;;;;;;;;;;;;;; ;; runtime procedures ;; ;;;;;;;;;;;;;;;;;;;;;;;; to go ask one-of turtles [ ifelse (color = blue) [ set color red set xcor (random-float 24) + 1 ] [ set color blue set xcor (- (random-float 24)) - 1 ] ] set urnA (count turtles with [color = blue]) set ratio (urnA / number-of-particles) tick end

There is only one version of this model, created over 10 years ago by Do Trong Thanh.

## Attached files

File | Type | Description | Last updated | |
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Ehrenfest Urn Model.png | preview | Preview for 'Ehrenfest Urn Model' | over 10 years ago, by Do Trong Thanh | Download |

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