在Netlogo中指定海龟的散布距离

Question

So for part of my model, I want my turtles (in this case, deer, specifically juvenile female deer) to "disperse" according to certain criteria. Here is what I have so far:

to move-dispersing-femjuvs
 ask femjuvs [
 let natal-range patches in-radius 5
 let density (count femadults-on natal-range + count maleadults-on natal- 
 range + count femjuvs-on natal-range + count malejuvs-on natal-range + 
 count infants-on natal-range)
 let chance-disperse 1 / (1 + exp(2.051 - (0.002605 * density)))
 if (random-float 1.001 < chance-disperse) [
 let mean-distance (18.703 + (0.02533 * density))

I believe this will give me the proportion of the female juveniles that will disperse, as well as the mean dispersal distance, taken from literature (I realize the if statement is incomplete, this is where I'm stuck). My question is, how do I get the "femjuvs" who are dispersing to actually move? They would move until they reach an unoccupied patch in a radius that does not overlap the "natal range". Ideally, I would want all of the distances of the femjuvs who do disperse to have a mean of "mean-distance". I have "dispersal-distance" as a "femjuvs-own" variable, but I haven't set it to any value.

Any help with any part of this problem is appreciated. Thank you!

Answer 1

Possibly use: "setxy" or "forward"

setxy

If the aim is to update a deer position over time, calculating its coordinates, setxy might be a good option. This isn't so much moving as it is adjusting its coordinates.

ask femjuvs [ setxy <xcor> <ycor> ] ; example

ask femjuvs [ let x-coordinate <some-long-computation>
              let y-coordinate <some-longer-computation>
              setxy x-coordinate y-coordinate ]

forward

To move a deer, there is a function called "forward" that can be invoked by femjuvs (turtle/breed context):

ask femjuvs [ forward <number> ]

It would move femjuvs n spaces in the direction it is facing, where is the number specified.

Possible additions: (* - relevant functions)

to move-dispersing-femjuvs
  ask femjuvs [
    let natal-range patches in-radius 5
    let density (count femadults-on ...) ; shortened for space

    * forward 1              ; move forward one
  ]
  ...
end

Also, if dispersing from a given point or coordinate is necessary, having the deer face the point and turn it 180 degrees could work.

ask femjuvs [ face <random-point> ; or facexy <xcor> <ycor>
              left 180  ]         ; turn the opposite direction
ask femjuvs [ forward 1 ]         ; disperse

One thing to note is that if the direction is not set by the developer, NetLogo will store a direction beforehand, which may or may not be helpful.

More details in : https://ccl.northwestern.edu/netlogo/docs/dictionary.html