calculating variance of a turtle-owned factor on a single patch in netlogo

问题

I'm trying to calculate the variance of a turtle owned factor on a single patch. In other words at a single patch I'd like to know the mean and variance of the factor among all turtles on that patch.

I know 'mean [FACTOR] of turtles-here' will give me the mean, but for some reason variance isn't working as well. Question 1: What is the proper syntax for asking a patch to output the variance of a turtle-owned factor?

I've worked up a super simple example model. Just paste this in for your code, then create 'setup' and 'go' buttons on the interface. It should have pink turtles seeking and stopping on black patches.

turtles-own
   [FACTOR]
patches-own
  [DEPTH]
to setup
  clear-all
  reset-ticks
  make_patches
  make_turtles
end

to go
  move
  if count (turtles with [DEPTH > 0]) = 0 [stop]
end

to make_patches
  ask patches [set depth 20 set pcolor green - 2]
  ask n-of 5 patches [set depth -50 set pcolor black]
end

to make_turtles
  create-turtles 10
  ask turtles 
  [
    set color pink 
    set size 2
    set xcor random max-pxcor
    set ycor random max-pycor
    set FACTOR random 100
  ] 
end

to move
  ask turtles[
    let D min [DEPTH] of patches in-radius 3
    let Dn min-one-of patches in-radius 3 [DEPTH]
    let LDe [DEPTH] of patch-here

ifelse DEPTH < 0
[
  move-to patch-here
  stop
]
[ifelse LDE > D AND D < 0
  [
    move-to DN
    stop
  ]
  [
    right random-float 150
    forward random 3
  ]
]
  ]
end

In the end I'd like to do a behavior-space experiment where at the end of each run every patch with DEPTH< 0 calculates and outputs the mean, standard deviation, and variance of FACTOR for turtles on that exact patch. My plan is to create a list of the sort

 ask patches with [DEPTH< 0] [set FACTOR_LIST (list ("[")(COORDINATES) (",") (VARIANCE_FACTOR) ("]") )]

where FACTOR_LIST is the exported list, COORDINATES is a list consisting of the x and y coordinates of the patch, and VARIANCE_FACTOR is the variance of the factor (which I'm asking how to do here). Question 2: Is there a more efficient way to get this list?

Thanks much!

回答1:

writing the question led me to the answer to the first one at least.

I changed:

patches-own
  [
    DEPTH
    DENSITY
    FACTOR_VARIANCE
    FACTOR_LIST
  ]
to go
  move
  if count (turtles with [DEPTH > 0]) = 0
   [
    final_tick
    ask patches with [DEPTH < 0] [show FACTOR_LIST]
    stop
    ]

end

and added a new procedure that calculated the variance and put it in a list I can call from the patch

to final_tick
  ask patches with [DEPTH < 0] [set DENSITY count turtles-here]
  ask patches with [DEPTH < 0 AND DENSITY <= 1] [set FACTOR_VARIANCE 0]
  ask patches with [DEPTH < 0 AND DENSITY > 1] [set FACTOR_VARIANCE (variance [FACTOR] of turtles-here)]
  ask patches with [DEPTH < 0] [set FACTOR_LIST (list (pxcor)(",")(pycor)(",")(FACTOR_VARIANCE))]
end

Would still like to know if anyone has a more efficient way of accomplishing this goal.

来源：https://stackoverflow.com/questions/40730974/calculating-variance-of-a-turtle-owned-factor-on-a-single-patch-in-netlogo

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