NetLogo-将沙堆模型中的沙粒分布到随机邻居

此代码与NetLogo沙堆模型的自适应相关。当每个斑块中的go晶粒数超过阈值（在本例中为3）时，晶粒将重新分布到周围的相邻区域。我正试图将一粒粮食重新分配给4个随机相邻的补丁

代码返回一个运行时错误，因为边缘的补丁程序不会包含所有8个邻居，因此当请求4个随机邻居时，它返回一个错误，说明无法从3个代理程序请求4个赎金代理，以此类推

我试图找到一段代码来解决这个问题

****代码如下*****

to-report stabilize [animate?]
  let active-patches patches with [ n > threshold ]

  ;; The number iterations the avalanche has gone for. Use to calculate lifetimes.
  let iters 0

  ;; we want to count how many patches became overloaded at some point
  ;; during the avalanche, and also flash those patches. so as we go, we'll
  ;; keep adding more patches to to this initially empty set.
  let avalanche-patches no-patches

  while [ any? active-patches ] [
    let overloaded-patches active-patches with [ n > threshold ]
    if any? overloaded-patches [
      set iters iters + 1

    ]
    ask overloaded-patches [
      set base-color fired-color
      ;; subtract 'threshold' amount from this patch
      update-n -4
      if animate? [ recolor ]
      ;; edge patches have less than four neighbors, so some sand may fall off the edge
      ask n-of 4 neighbors [
        update-n 1
        if animate? [ recolor ]
      ]
    ]
    if animate? [ display ]
    ;; add the current round of overloaded patches to our record of the avalanche
    ;; the patch-set primitive combines agentsets, removing duplicates
    set avalanche-patches (patch-set avalanche-patches overloaded-patches)
    ;; find the set of patches which *might* be overloaded, so we will check
    ;; them the next time through the loop
    set active-patches patch-set [ neighbors ] of overloaded-patches
  ]
  report (list avalanche-patches iters)
end  

---

不要询问4个邻居，而是询问

min list 4 count neights

：

ask n-of (min list 4 count neighbors) neighbors [ 
  ... 
]

但是从模型的角度来看，在表的边缘会有不同的再分配，所以这不是一个好主意。也许更好的做法是先创建一个包装好的世界，然后手动“推”掉桌子上的谷物：选择4个邻居，只调用那些具有相近pxcor和pycor的邻居。剩下的就不在桌上了

如果世界被包裹（水平和垂直），我们总是可以选择4个邻居：

let selected-neighbors n-of 4 neighbors 

在这4个邻居中，只有真正的邻居在桌子上

set selected-neighbors selected-neighbors with [ 
  (abs (pxcor - [ pxcor ]  of myself) < 2) 
  and
  (abs (pycor - [ pycor ]  of myself) < 2) 
  ] 

ask selected-neighbors [
 ....
 ]

用[
（我的abs（pxcor-[pxcor]）<2）
和
（abs（pycor-[pycor]我自己）<2）
] 
询问选定的邻居[
....
]