---gaslab gas in a box.nlogo

NETLOGO

globals [
  fast medium slow                ;; current counts
  avg-speed avg-energy            ;; current averages
  avg-speed-init avg-energy-init  ;; initial averages
  clock vsplit vclock             ;; clock variables
  box-edge                        ;; patch coords of box's edge
  fade-needed?
]

turtles-own [
  speed mass energy                     ;; turtle info
  v1t v1l tmp-turtle                    ;; collision info (turtle 1)
  heading2 mass2 speed2 v2t v2l turtle2 ;; collision info (turtle 2)
  theta                                 ;; collision info (both turtles)
]

to setup
  ca
  set box-edge (round (screen-edge-x * box-size / 100))
  make-box
  set fade-needed? false
  set clock 0
  set vclock 0
  cct number 
  [ set speed initspeed
    set mass initmass
    if who != 0
      [ random-position ]
    rt random-float 360
    set shape "circle"
    recolor
  ]
  update-variables
  set avg-speed-init avg-speed
  set avg-energy-init avg-energy
  setup-plots
  setup-histograms
  do-plotting
  do-histograms
end

to update-variables
  ask turtles
    [ set energy (0.5 * speed * speed * mass) ]
  set medium count turtles with [color = green]
  set slow    count turtles with [color = blue]
  set fast    count turtles with [color = red]
  set avg-speed  mean values-from turtles [speed]
  set avg-energy mean values-from turtles [energy]
  set vsplit ceiling max values-from turtles [speed]
end

to recalculate-vsplit
  ;; this needs to be done without-interruption to be sure that nothing tries to
  ;; use vsplit or vclock before they've been recalculated
  without-interruption
  [ set vsplit 2 * vsplit
    set vclock 2 * vclock
  ]
end

to go
  ask turtles [ bounce ]
  ask turtles [ move ]
  if trace?
    [ ask turtle 0
        [ stamp gray
          set fade-needed? true ] ]
  set vclock (vclock + 1)
  if (vclock = vsplit)
  [ set clock (clock + 1)
    set vclock 0
    update-variables
    do-plotting
    do-histograms
    if fade-needed? [ fade-patches ]
  ]
end

to bounce  ;; turtle procedure
  locals [new-px new-py]
  ; if we're not about to hit a wall (yellow patch),
  ; we don't need to do any further checks
  if pcolor-of patch-ahead 1 != yellow [ stop ]
  ; get the coordinates of the patch we'll be on if we go forward 1
  set new-px pxcor-of patch-ahead 1
  set new-py pycor-of patch-ahead 1
  ; check: hitting left or right wall?
  if (abs new-px = box-edge)
    ; if so, reflect heading around x axis
    [ set heading (- heading) ]
  ; check: hitting top or bottom wall?
  if (abs new-py = box-edge)
    ; if so, reflect heading around y axis
    [ set heading (180 - heading) ]
end

to move  ;; turtle procedure
  while [(speed / vsplit) >= 1.0]
  [ recalculate-vsplit ]
  jump (speed / vsplit)
  check-for-collision
end

to check-for-collision  ;; turtle procedure
  if count other-turtles-here = 1
    [ set tmp-turtle random-one-of other-turtles-here
      if ((who > who-of tmp-turtle) and (turtle2 != tmp-turtle))
        [ collide ]
    ]
end

to collide  ;; turtle procedure
  get-turtle2-info
  calculate-velocity-components
  set-new-speed-and-headings
end

to get-turtle2-info  ;; turtle procedure
  set turtle2 tmp-turtle
  set mass2 mass-of turtle2
  set speed2 speed-of turtle2
  set heading2 heading-of turtle2
end

to calculate-velocity-components
  locals [vcm]  ;; CM vel. along dir. theta
  set theta (random-float 360)
  set v1l (speed * sin (theta - heading))
  set v1t (speed * cos (theta - heading))
  set v2l (speed2 * sin (theta - heading2))
  set v2t (speed2 * cos (theta - heading2))
  set vcm (((mass * v1t) + (mass2 * v2t)) / (mass + mass2))
  set v1t (vcm + vcm - v1t)
  set v2t (vcm + vcm - v2t)
end

to set-new-speed-and-headings  ;; turtle procedure
  set speed sqrt ((v1t * v1t) + (v1l * v1l))
  set heading (theta - (atan v1l v1t)) 

  set speed-of turtle2 sqrt ((v2t * v2t) + (v2l * v2l))
  set heading-of turtle2 (theta - (atan v2l v2t))

  recolor
  ask turtle2 [ recolor ]
end

to recolor  ;; turtle procedure
  ifelse speed < (0.5 * initspeed)
    [ set color blue ]
    [ ifelse speed > (1.5 * initspeed)
        [ set color red ]
        [ set color green ] ]
end

to fade-patches
  locals [trace-patches]
  set trace-patches patches with [(pcolor != yellow) and (pcolor != black)]
  ifelse any? trace-patches
    [ ask trace-patches
      [ set pcolor ( pcolor - 0.4 )
        if (not trace?) or (round pcolor = black)
          [ set pcolor black ] ] ]
    [ set fade-needed? false ]
end

to make-box
  ask patches with [((abs pxcor = box-edge) and (abs pycor <= box-edge)) or
                    ((abs pycor = box-edge) and (abs pxcor <= box-edge))]
    [ set pcolor yellow ]
end

to random-position ;; turtle procedure
  setxy ((1 - box-edge) + random-float (2 * box-edge - 2))
        ((1 - box-edge) + random-float (2 * box-edge - 2))
end

;;; plotting procedures
to setup-plots
  set-current-plot "Speed Counts"
  set-plot-y-range 0 number
end

to do-plotting
  set-current-plot "Speed Counts"
  set-current-plot-pen "fast"
  plot fast
  set-current-plot-pen "medium"
  plot medium
  set-current-plot-pen "slow"
  plot slow
end

to setup-histograms
  set-current-plot "Speed Histogram"
  set-plot-x-range 0 (initspeed * 2)
  set-plot-y-range 0 ceiling (number / 6)
  set-current-plot-pen "medium"
  set-histogram-num-bars 40
  set-current-plot-pen "slow"
  set-histogram-num-bars 40
  set-current-plot-pen "fast"
  set-histogram-num-bars 40
  set-current-plot-pen "init-avg-speed"
  draw-vert-line avg-speed-init

  set-current-plot "Energy Histogram"
  set-plot-x-range 0 (0.5 * (initspeed * 2) * (initspeed * 2) * initmass)
  set-plot-y-range 0 ceiling (number / 6)
  set-current-plot-pen "medium"
  set-histogram-num-bars 40
  set-current-plot-pen "slow"
  set-histogram-num-bars 40
  set-current-plot-pen "fast"
  set-histogram-num-bars 40
  set-current-plot-pen "init-avg-energy"
  draw-vert-line avg-energy-init
end

to do-histograms
  set-current-plot "Speed Histogram"
  set-current-plot-pen "medium"
  histogram-from turtles with [color = green] [speed]
  set-current-plot-pen "slow"
  histogram-from turtles with [color = blue] [speed]
  set-current-plot-pen "fast"
  histogram-from turtles with [color = red] [speed]
  set-current-plot-pen "average-speed"
  plot-pen-reset
  draw-vert-line avg-speed

  set-current-plot "Energy Histogram"
  set-current-plot-pen "medium"
  histogram-from turtles with [color = green] [energy]
  set-current-plot-pen "slow"
  histogram-from turtles with [color = blue] [energy]
  set-current-plot-pen "fast"
  histogram-from turtles with [color = red] [energy]
  set-current-plot-pen "average-energy"
  plot-pen-reset
  draw-vert-line avg-energy
end

; draws a vertical line at xval on the current-plot with the current plot-pen
to draw-vert-line [xval]
  plotxy xval plot-y-min
  plot-pen-down
  plotxy xval plot-y-max
  plot-pen-up
end


; *** NetLogo Model Copyright Notice ***
;
; This model was created as part of the project: CONNECTED MATHEMATICS:
; MAKING SENSE OF COMPLEX PHENOMENA THROUGH BUILDING OBJECT-BASED PARALLEL
; MODELS (OBPML).  The project gratefully acknowledges the support of the
; National Science Foundation (Applications of Advanced Technologies
; Program) -- grant numbers RED #9552950 and REC #9632612.
;
; Copyright 1998 by Uri Wilensky. All rights reserved.
;
; Permission to use, modify or redistribute this model is hereby granted,
; provided that both of the following requirements are followed:
; a) this copyright notice is included.
; b) this model will not be redistributed for profit without permission
;    from Uri Wilensky.
; Contact Uri Wilensky for appropriate licenses for redistribution for
; profit.
;
; This model was converted to NetLogo as part of the project:
; PARTICIPATORY SIMULATIONS: NETWORK-BASED DESIGN FOR SYSTEMS LEARNING IN
; CLASSROOMS.  The project gratefully acknowledges the support of the
; National Science Foundation (REPP program) -- grant number REC #9814682.
; Converted from StarLogoT to NetLogo, 2001.  Updated 2002.
;
; To refer to this model in academic publications, please use:
; Wilensky, U. (1998).  NetLogo GasLab Gas in a Box model.
; http://ccl.northwestern.edu/netlogo/models/GasLabGasinaBox.
; Center for Connected Learning and Computer-Based Modeling,
; Northwestern University, Evanston, IL.
;
; In other publications, please use:
; Copyright 1998 by Uri Wilensky.  All rights reserved.  See
; http://ccl.northwestern.edu/netlogo/models/GasLabGasinaBox
; for terms of use.
;
; *** End of NetLogo Model Copyright Notice ***
@#$#@#$#@
GRAPHICS-WINDOW
269
10
688
450
49
49
4.1313131313131315
1
10
1
1
1
0

CC-WINDOW
5
402
798
497
Command Center

MONITOR
188
53
269
102
clock
clock
0
1

MONITOR
188
171
269
220
avg-speed
avg-speed
2