I wanna make turtles do directed movements in NetLogo. Let's say we have a specific area as blue-patches where turtles can only survive within this area. They cannot escape from this area. And for each turtle it wanna move toward to lower local density with a specific speed (a minimum number of turtles within an area with a specific radius).
I generate a variable for patches as local-density.
and use
let ideal-destination min-one-of blue-patches [ count turtles in-radius 5 ]
face ideal-destination
to get the direction of movement. But the problem is with a specific speed they can escape from the constrained area. How can I let them stop at the edge of the constrained area?
For moving turtles in a constraint area with a specific speed, we can use patch-ahead to check:
ifelse patch-ahead speed != nobody
[ifelse [pcolor] of patch-ahead high-speed = white ;;the color of outside of the area
[ fd 0 ]
[ fd speed ] ]
[ fd 0 ]
Related
I'm trying to model predators hunting prey through a world filled with obstacles. In an obstacle free world, the predators go on random walks until prey fall within a certain detection radius (react-D), and then move towards the prey to capture. I guess there may be several ways to handle obstacles that block line of sight, but my initial efforts are along the following lines:
ifelse any? prey in-radius react-D
[let target min-one-of prey in-radius react-D [distance myself]
face target
...move towards target if it's closer than the nearest obstacle (blue patch) ahead
]
[continue to random walk, avoiding obstacles
]
The first condition of ifelse may need another ifelse. In any case I think I just need a distance of the nearest blue patch ahead to compare with the target distance, but it's not clear to me how I can get that from patch-ahead.
It would be nicer if I could put all this into the test of the first ifelse, but something like the following doesn't allow for patches that aren't blocking line of sight to the prey:
ifelse any? prey in-radius react-D and min-one-of (patches in-radius react-D with [pcolor = blue])[distance myself] > min-one-of (prey in-radius react-D) [distance myself]
Line of sight is actually really tricky to model in NetLogo. At the moment I do it by creating a turtle (invisible, separate breed called crawler) where the agent is that is looking and have the crawler move ahead in small steps checking the colour of the patch that it is on. That goes inside a while loop and the crawler stops when it finds the wrong colour or when it gets to the target distance. the crawler has to take small steps because crossing over the corner of a patch should still block it and it's a trade-off between resolution (how small the crawler step is) against efficiency.
You can almost certainly do the same thing by creating a patch-set as the union of patches found with patch-ahead of multiple distances like 0.1, 0.2, .... and then checking any? over that patch-set
My current solution, giving patches-own [ ob ] values of 1 to all obstacle patches, then using while to detect obstacles ahead:
to detect-ahead
let dist 1
let last-patch patch-here
while [dist <= react-D] [
let p patch-ahead dist
if p != last-patch and [ob] of p = 1 [
ask p [ sprout-markers 1 [ set color yellow ] ]
set last-patch p
]
set dist dist + 1
]
end
Then it should simply be a case of comparing min-one-of the marker agent set with the target. Obviously smaller increments would be good, as JenB says.
I sprouted my turtles over the patches and in the 'go' I want each turtle to calculate if another turtle is too close (based on a certain threshold of X meters/patches). If another turtle is too close, i want the turtle to become 'dissatisfied'.
Movements of the turtles are not required.
What is the best way to do this? The only piece of code for the go procedure I have so far is as follows:
to go
ask n-of initial-number-tourists (patches with [ lagoon_proximity = 1])
[
sprout 1 [
set color black
set size 10
]
]
tick
end
Kind regards!
Your code is creating more turtles and doesn't have anything about checking distances so it is not clear how it is related to the problem you are trying to solve. However, the following code measure the distance to the nearest turtle and prints a message if that is less than 5.
ask turtles
[ let nearest min-one-of turtles [distance myself]
if distance nearest < 5 [ show "I feel crowded" ]
]
I'm trying to add a condition that doesn't allow an agent to cross over a road. The road patches are set to color red. I can't seem to figure out how to get this condition to work. I ultimately want the agent to turn around if the road is in the patch ahead. Here is my net logo code so far.
to go
ask turtles [
move
]
tick
if ticks >= 60 [stop]
end
to move
ifelse random-float 1 < q
[
ifelse random-float 1 < w
[let target-patch max-one-of neighbors [veg-suitability]
face target-patch]
[let target-patch max-one-of neighbors [pelev]
face target-patch]
]
[
ifelse [pcolor] of patch-ahead 1 = red
[lt random-float 180]
move-to one-of neighbors
ldd-normal
]
end
to ldd-normal
let ldd-distance (ldd-scale)
fd ldd-distance
end
The logic of your move procedure is a bit confused I think. First you have a random chance to either move to a patch with a higher value of a variable of interest (with the uphill primitive) or, if the random draw fails, it moves to a random neighbour. If you don't want it to move onto a red patch then you need to test if the patch that is chosen is red, but you just move it without checking.
After you have moved the turtle, you then check the colour of patch-ahead. Your problem here is that patch-ahead depends on the direction the turtle is facing, which has nothing to do with the direction it has already been moving. You either make it turn (though it may not turn enough) OR move forward. So it never actually moves away.
I can't give you an actual answer because I don't know what your logic is supposed to be. But you could look at structures like:
move-to one-of neighbors with [pcolor != red]
Or, if there are enough red patches that it is possible that there aren't any non-red neighbours (which would cause an error if you tried to move to one), you could use:
let okay-patches neighbors with [pcolor != red]
if any? okay-patches [move-to one-of okay-patches]
Another option is that you only meant to face rather than move to the patch in the first sections of code, then test whether it is facing a red patch and turn around if it is.
I'm trying to set turtles heading equal to leader's heading and at the same all turtles including leaders must avoid obstacle( avoid_obstacles function). My problem is, when i add the set heading code
in flock function:
[set heading [heading] of one-of nearby-leaders ]
it cause my avoid-obstacle code to break. if i comment out this code, avoid obstacle work fine. below is my complete code.
to go
set time-to-evacuate time-to-evacuate + 1
ask turtles [check fd 0.1]
ask turtles [avoid_obstacles fd 0.1]
ask turtles with [pcolor = red][die] ;;turtles exit thru red door will die
if all? turtles [ pcolor = red ] ;; stop simulation
[ stop ]
tick
end
to check
if not leader?
[let beings-seen patches in-cone vision vision-angle with [pcolor = red]
ifelse any? beings-seen
[let target one-of beings-seen face target fd 1 ]
[flock]]
if leader?
[let beings-seen patches in-cone leader-vision leader-vision-angle with [pcolor = red]
ifelse any? beings-seen
[let target one-of beings-seen face target fd 1 ]
[flock]]
end
to flock
let nearby-leaders turtles with [leader? ]
if any? nearby-leaders in-radius vision
[ set heading [heading] of one-of nearby-leaders ]
end
to avoid_obstacles ;; all obstacles set as green patches
let i 1
while [[pcolor] of patch-ahead i != green and i <= vision]
[set i (i + 1) ]
if ([pcolor] of patch-ahead i = green)
[
ifelse [pcolor] of patch-at-heading-and-distance (heading - 20) i + 1 = green
[
ifelse [pcolor] of patch-at-heading-and-distance (heading + 20) i + 1 = green
[
ifelse random 1 = 0
[ rt 30 ]
[ lt 30 ]
]
[ rt 60 ]
]
[lt 60]
]
end
can somebody point what wrong with my code
First of all, consider abandoning the concept of having "leaders" as such. In crowd escape panic situations, they don't stop and hold elections. LOL. I don't know what your model is trying to model, so I have no suggestions here. My model "
Anyway, what your "followers" need to do is integrate to desires, the desire to go the same way as the leader, and the desire to avoid obstacles.
For the first, the follower simply needs a place to remember the "desired" direction. So, rather than set heading directly, you store the heading of the leader./ Then you perhaps use that heading to influence the movement around obstacles.j
For the second, well, obstacle avoidance is a complex discussion on its own. Whatever you have put together, you need to modify it so that it takes the "desired" heading into account, while still effectively avoiding obstacles. This is can be very difficult to do simply.
My model "homing particles 2009" uses one method. This model is designed to explore a particular homing/avoidance behavior. When a particle can't move in the desired direction, it is allowed to move in a limited number of other directions, instead.
Here is the link: http://www.turtlezero.com/models/view.php?model=homing-particles_2009
Unless you have added http://www.turtlezero.com to your list of allowed sites in your Configure Java console (not recommended, but you can trust me, right?), you will not be able to run my models in the browser. I haven't checked what that model needs to run in NetLogo 5.
The ultimate solution to that problem may be to use a path-finding algorithm, like a* (a-star).
In that case you provide your follower with a preferred destination (and that can be vaguely defined as "a point somewhere in 'that' direction"), and the route-planner algorithm plots a route. You can make the route-planner unaware of obstacles until they are "visible" or whatever you define (for example, in a press of bodies, a follower might not be aware of an obstacle until stumbled upon).
Hope this helps!
let pop area * density
distribute-turtles
to distribute-turtles [ pop box ]
if (pop > count box) [ error "Box can't hold all turtles!" ]
ask n-of pop box [sprout-inboxturtles 1[
set color blue
set exit true ;ignore
set alpha alpha-exit ;ignore
set beta beta-exit ;ignore
set size 0.9
]
]
end
The above code distributes turtles on patches.
box-patches
pop-number of turtles
I will create turtles such in accordance to the density within the box such that:
a.) no 2 turtles have the same centre, therefore there could more than 2 turtles per patch but shouldn't have the same centre.
The turtles already have random headings so if you have them go forward a random float less than .5 they will have unique coordinates.
fd random-float .5
Aesthetically the turtle size should be small enough to see each.
Remember turtles-here will report all turtles on the patch.