导出绘图时无数据

Question

我正在使用Railsback和Grimm一书学习NetLogo。我试图在Mac上使用NetLogo 5.1.0复制一些模型。

我创建了一个图表来显示走廊宽度如何随着蜱变化。我可以在图上看到这条线，但是当我将数据导出到.csv文件时，我得不到关于该图的信息：

    "export-plot data (NetLogo 5.1.0)"
    "ch04_butterfly_v2.nlogo"
    "01/02/2015 14:52:55:280 -0600"

    "MODEL SETTINGS"
    "number","q"
    "50","0.48"

    """Corridor Width"""
    "x min","x max","y min","y max","autoplot?","current pen","legend open?","number of pens"
    "0","1","0","100","true","""""","false","0"

    "pen name","pen down?","mode","interval","color","x"

有什么想法吗？谢谢你的耐心等待。

我的代码：

globals [ ] 
patches-own [ elevation used?]
turtles-own [ start-patch ]

to setup
ca

file-open "ElevationData.txt" 
while [not file-at-end?]
  [
    let next-x file-read 
    let next-y file-read
    let next-elevation file-read
    ask patch next-x next-y [set elevation next-elevation]
   ]
file-close  

let min-elevation min [elevation] of patches 
let max-elevation max [elevation] of patches

ask patches [    
    set pcolor scale-color green elevation min-elevation max-elevation
    set used? false
   ]

crt number [
    set size 2
    setxy 85 95
    pen-down
    set start-patch patch-here
   ]  
reset-ticks
end

to go
  ask turtles [move]
  plot corridor-width
tick
if ticks >= 1000
   [ 
    export-plot "corridor width" (word "corridor-output-for-q-" q ".csv")
    stop 
   ]

end

to move 
  if elevation >= [elevation] of max-one-of neighbors [elevation]
  [stop]
  ifelse random-float 1 < q
  [ uphill elevation ]
  [ move-to one-of neighbors]
  set used? true
end

to-report corridor-width
  let patch-visited count patches with [used?]
  let mean-distance mean [distance start-patch] of turtles 
  ifelse mean-distance > 0
  [report patch-visited / mean-distance]
  [report]
end