NetLogo中计算匹配变量海龟意见平均值时MEAN函数报错求助

问题说明 #

运行模型setup时触发错误：

MEAN expected input to be a list but got the number #### instead.
（注：####为每次运行时随机变化的浮点数）

模型执行流程：

• 定义districts种群，生成地图上不同颜色的区域。
• 创建turtles：随机分配opinion值、linked（0或1），并获取所在patch对应的district实例存入mydistrict变量。
• 调用org-effects-mean过程，意图计算同区域内所有linked=1的海龟的opinion平均值，赋值给海龟的org-influence-opinion变量，但该过程触发上述错误。

错误原因 #

org-effects-mean过程的写法逻辑错误：

set org-influence-opinion ([ mean opinion ] of turtles with [mydistrict = [mydistrict] of myself and linked = 1])

这段代码是让每个符合条件的海龟分别执行mean opinion操作，但单个海龟的opinion是单个数值，并非列表，而MEAN原语要求输入必须是列表，因此触发错误。

解决方案 #

正确逻辑是先获取所有符合条件的海龟的opinion值组成的列表，再对列表求平均值。调整org-effects-mean过程写法如下：

to org-effects-mean
  ask turtles [
    if linked = 1 [
      let target-turtles turtles with [mydistrict = [mydistrict] of myself and linked = 1]
      set org-influence-opinion mean [opinion] of target-turtles
    ]
  ]
end

代码解释 #

1. 用let target-turtles筛选出当前海龟所在区域、且linked=1的所有海龟集合。
2. 用[opinion] of target-turtles提取这些海龟的opinion值，得到数值列表。
3. 对列表执行mean计算，将平均值赋值给org-influence-opinion。

修正后的完整代码 #

breed [ districts district ]

turtles-own [ linked mydistrict opinion org-influence-opinion ]
districts-own [ district-id district-patches district-turtles ]
patches-own [ pdistrict ]

globals [ num-districts ]

to setup
  ca
  set num-districts 4
  grow-districts
  create-turtles 100 
  ask turtles [
    setxy random-xcor random-ycor
    set linked one-of [ 0 1 ] 
    set mydistrict [pdistrict] of patch-here
    set opinion random-float 1
  ]
  org-effects-mean
end

to grow-districts ;; Barranca addition
  Create-districts num-districts
  [
    ;; set district breed shape
    set shape "arrow"
    __set-line-thickness 1
    set size .4
    ;; Set randomish location...
    setxy random-xcor random-ycor
    ;;; tag this patch
    Set pdistrict self
    ;set district-id district-id + 1
    set color (deep-color-1 who)
    set pcolor color

  ]
  ;; expand districts
  While [ any? patches with [ pdistrict = 0 ] ]
  [
    Ask patches with
    [ pdistrict != 0  and any? Neighbors with [ pdistrict = 0 ] ]
    [ Ask neighbors with
      [ pdistrict = 0 ]
      [ set pdistrict [ pdistrict] of myself
        Set pcolor [ color ] of pdistrict
      ]
    ]
  ]
end

to org-effects-mean
  ask turtles [
    if linked = 1 [
      let target-turtles turtles with [mydistrict = [mydistrict] of myself and linked = 1]
      set org-influence-opinion mean [opinion] of target-turtles
    ]
  ]
end

to-report deep-color-1 [ value ]
  report (
  red + 10 * (value mod 13) ;; base netlogo color
  ;; shift up or down
  +  .5 * ( (int (value / 13 )) mod 2 * 2 - 1) ;; alternate normal -1, +1
  ;; increase difference (gets brighter and darker)
  * (1 + int ( value / ( 2 * 13 )))
  )
end

内容的提问来源于stack exchange，提问作者Abe