I have a model that tracks energy levels in sheep, which I have defined as a breed. I have set up a monitor to calculate the mean energy level for the sheep, but need to consider what happens if there are no sheep at some point. I have tried numerous variations, the simplest of which is:
ifelse (any? sheep) ["NA"] [mean [energy] of sheep]
Unfortunately, I keep getting the error
Expected reporter.
I can work around this by creating a new global variable and reporter in the code, but this seems to be a bit of a waste. Am I doing something wrong or are there limitations on what kind of calculations can be done in a monitor on the Interface? If so, where are these limitations summarized?
Answer in three steps:
Difference between ifelse and ifelse-value
You are getting a syntax error there because a monitor expects a reporter, but ifelse is made to handle commands. The reporter version of ifelse is ifelse-value. If you just change ifelse to ifelse-value in your example, you see that you don't get any syntax error anymore. However, you will also see that if you do so and start your model with sheep having their energy, the monitor will show NA - see next point.
Correct use of any?
This happens because you are using any? the other way around. As you can see, any? reports true if the agentset is not empty. This means that the following reporter:
ifelse-value (any? sheep) ["NA"] [mean [energy] of sheep]
will report "NA" when there are sheep in the model, because that is the first reporter block.
Switch to:
ifelse-value (any? sheep) [mean [energy] of sheep] ["NA"]
and you have what you want. Just as in English: "If there are any sheep, do the calculation, else, this does not apply".
In any case, this does the job but it is superflous - see next point.
What monitors can do
Monitors are able to handle some of their reporters' runtime errors. You can simply put mean [energy] of sheep in your monitor and it will automatically show N/A when there are no sheep, without the need for you to handle the case.
Related
Looking for a way to store a turtle length of stay in the model after they have left the model. My model runs for several months and a few thousand turtles enter, undergo process then leave the area. It's complicate model (it's a hybrid DES and ABM) so I've tried to reproduce the simple bit below.
Turtles will be created at every tick and given a random length of stay but will only be able to begin process when they move to the right area (area-name) and when their time is up they leave the area. Their time-in-system reflects the wait for the area and the length-of-stay which I want to save once they're complete. If I leave them in the model it starts to break down after a couple of months and I suspect this is because the model has too many turtles still in the system for calculation and is inefficient.
go
create turtles 2
[
set time-in-system 0
set length-of-stay ceiling ((random-normal 48 4) + ticks)]
set shape "person"
if any? area-name with [not any? turtles-here]
[move-to one-of area-name]
]
undergo-process
end
to-undergo-process
ask turtles with [shape = "person"]
[
set time-in-system time-in-system + 1
]
ask turtles-on area-name
[if ticks = length-of-stay
[set shape "dot"
move-to exit-door]
end
I can then plot and see in realtime to make sure it is working
histogram time-in-system of turtles with [shape = "dot"]
but can't seem to figure out how to store them as unique values for plotting after the model has run and I have a dataset of outcomes without keeping them alive in the model. The real-time plot isn't necessary as long as I can store the unique values after they have left
If I ask them to die then I lose the unique values in the histogram. I don't want a tally of all values but each turtle's unique value at the end of the process after they left - at the moment the only solution I have to storing them is as an agent-set that stays alive in the exit-door patch but this takes up a lot of calculation power as the model progresses for months...
There may be a really simple command for this but I've been going round in circles through the programming manual trying to find it. Any tips appreciated
You should create a list storing the values of turtles that left.
Isolating only the code that is relevant for this purpose, it would be something like:
globals [
times
]
to setup
set times (list)
end
to leave-simulation ; This being executed by turtles.
set times lput (time-in-system times)
die
end
If your program is going to run for actual months, I recommend you use the file-write command to store your data. This way the data is preserved if the program halts for any reason; it gives you much more freedom to do the analysis you want without running the full simulation again.
If you write to a .csv (comma separated value) file, you can use almost any program (excel, R, matlab, python, C# or back to netlogo) to plot a histogram.
I'm writing a program that is testing the ability of turtles to navigate in an environment. This line of code has two checks. I want it to kill off the oldest turtle that has made the least amount of progress. It does what it is supposed to, but the program slows down dramatically, creating little hiccups every time it makes this check. I was wondering if someone knew a better way to go about this or make this line more efficient. Thanks!
ask one-of turtles with [XCOR = min [XCOR] of turtles with [age = max [age] of turtles]] [
die]
First of all, there are primitives that are specifically finding the turtles with maximum or minimum values of some variable using min-one-of or with-min. So your code would look something like this I think:
ask min-one-of (turtles with-max [age]) [xcor] [...]
I suspect that would solve your efficiency problem, since it may well be because of implicit brackets not being where you think they are so it's trying to loop everything a couple of times. But a much cleaner to read version that would solve the efficiency problem is to specifically limit the position loop to those who are oldest and then choose the lowest position from that set.
let old-turtles turtles with-max [age]
ask min-one-of old-turtles [xcor] [...]
I have a list of parcel agents. but I will kill the parcels periodically. However, the list is still recording someting like this: [nobody nobody nobody nobody nobody nobody nobody nobody], and overtime the running of the model is getting slower and eventually pop up message "your model is too large to run with available memory"
In this case, are the dead agents (i.e. nobody) still treated as an agents that consumes much of the memory? what if it is a pure list of numbers or strings? would it cause the same OOM issue? how big the list can be in Netlogo and any uppper limit?
From, the NetLogo dictionary for die: If you have a list of agents and the agent dies, then the agent is removed from any agentset and:
The agent will disappear from any agentsets it was in, reducing the size of those agentsets by one.
Any variable that was storing the agent will now instead have nobody in it
The dead agents are not consuming resources, but the list is (as you have found by printing out the list). You can see this with the following model:
globals [mylist myagentset]
to setup
clear-all
create-turtles 1
set mylist sort-on [who] turtles
set myagentset turtles
reset-ticks
end
to go
create-turtles 1
[ set myagentset (turtle-set myagentset self)
]
set mylist lput one-of turtles mylist
ask one-of turtles [die]
type "turtles: " print count turtles
type "list: " print length mylist
type "agentset: " print count myagentset
tick
end
If you want the dead turtle to be removed from the list, you need to explicitly do so with remove-item. The same is true of lists of numbers, strings etc.
Alternatively, if the list doesn't need to be maintained over ticks, but can be reconstructed (eg if it is a sorted list of the turtles agentset), you could create it each tick and that list would only contain turtles that are alive.
The monitor (below) is continually running and generating a random list of output, even though there is no tick activity.
Questions: Should it be continually running? Is there a way to monitor the list on the interface without the continual random output?
Code
to go
crt 100 [fd random 14 + 1]
end
to-report report-red-turtles
report [who] of turtles with [color = red]
end
To run:
On the interface, create a monitor report-red-turtles and a simple go button
It is by design that "Monitors automatically update several times per second". It's a convenient design in most cases, but can also have some weird consequences (be careful never to have side effects in monitor code!)
What happens in your case is that
[who] of turtles with [color = red]
produces different output each time it runs: the list produced by of is always in random order.
To get around this fact, you have two options.
Remove the randomness: sort [who] of turtles with [color = red].
Use a global variable (e.g. red-turtles), update it once per tick, and display that in your monitor.
It's a trade-off between simplicity and speed: the first option is simpler and cleaner, but more computationally expensive.
I am currently making a simulation (for homework) using genetic algorithms. What I want to do is compare the fitness of agents on a specific patch and the one with the lowest fitness will die.
I have scoured the net and found this code: if any? breed1-here with [fitness > fitness-of myself] [die]]
But this doesn't seem to work and now I'm completely out of ideas.
let goner min-one-of breed1-here [fitness]
if is-turtle? goner [ ask goner [ die ] ]`
the is-turtle? check is necessary because the patch might be empty.
Yes, that code is from an old version of the NetLogo language. That line of code should be re-written as:
if any? breed1-here with [fitness > [fitness] of myself] [die]]
Of course, that code will kill all turtles in a patch except for the one(s) with maximum fitness, which is not exactly what you want.