Feedback from users is very valuable to us in designing and improving NetLogo. We’d like to hear from you. (See Contacting Us.)
patch-ahead 1 is reporting the same patch my turtle is already standing on. Why?random-float 1 might return 0 but will never return 1. What if I want 1 to be included?The “Logo” part is because NetLogo is a dialect of the Logo language.
“Net” is meant to evoke the decentralized, interconnected nature of the phenomena you can model with NetLogo, including network phenomena. It also refers to HubNet, the multiuser participatory simulation environment included in NetLogo.
If you use or refer to NetLogo, HubNet or a model from the NetLogo models library, we ask that you cite it as follows:
NetLogo itself: Wilensky, U. 1999. NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University. Evanston, IL.
HubNet: Wilensky, U. & Stroup, W., 1999. HubNet. http://ccl.northwestern.edu/netlogo/hubnet.html. Center for Connected Learning and Computer-Based Modeling, Northwestern University. Evanston, IL.
The correct citation is included in the “Credits and References” section of each model’s Info tab.
NetLogo was first created in 1999 by Uri Wilensky at the Center for Connected Learning and Computer-Based Modeling, then at Tufts University in the Boston area. NetLogo grew out of StarLogoT, which was authored by Wilensky in 1997. In 2000, the CCL moved to Northwestern University, in the Chicago area. NetLogo 1.0 came out in 2002, 2.0 in 2003, 3.0 in 2005, 4.0 in 2007, 4.1 in 2009, and 5.0 in 2012.
NetLogo is written mostly in Scala, with some parts in Java. (Scala code compiles to Java byte code and is fully interoperable with Java and other JVM languages.)
The original StarLogo began at the MIT Media Lab in 1989 and ran on the Connection Machine. Later versions were developed for Macintosh computers: MacStarLogo (1994, MIT) and StarLogoT (1997, Tufts).
Today there are two StarLogo descendants under active development: NetLogo (from the CCL at Northwestern University) and StarLogo TNG (from MIT). NetLogo is the most widely used agent-based modeling environment in both education and research. StarLogo TNG is distinguished by its programming interface based on colored blocks.
NetLogo is free, open source software under the GPL (GNU General Public License), version 2, or (at your option) any later version.
Commercial licenses are also available. To inquire about commercial licenses, please contact Uri Wilensky at uri@northwestern.edu.
The source code is on GitHub, here. Development discussion is on the netlogo-devel group.
The User Manual is published under a Creative Commons Attribution-ShareAlike license (CC BY-SA 3.0).
Source code for all of the extensions bundled with NetLogo is on GitHub, here. Most of the extensions are in the public domain (CC0 notice). Other extensions are released under open source licenses. See each extension’s README for details.
The Code Examples in the Models Library are in the public domain (CC0 notice).
The rest of the models in the Models Library are provided under a variety of licenses. Some are public domain and some are open source, but most are under the Creative Commons Attribution-ShareAlike license (CC BY-NC-SA), which is not an open source license, though the models are free for noncommercial distribution and use.
See each model’s Info tab to check its particular license.
The models are in a public Git repository here.
We offer workshops from time to time. If a workshop has been scheduled, we will announce it on the NetLogo Users Group.
The CCL has published a textbook (written by the author of NetLogo) that gives an introduction to agent-based modeling methods using NetLogo. It goes step by step with coding examples how to design, build, revise, and analyze models. And it presents some advanced techniques.
See www.intro-to-abm.com for more information on that textbook.
See the Textbooks section of our Resources page.
We at the CCL have hoped to write several more NetLogo textbooks. These could be aimed at different audiences, such as: middle school, high school, undergraduate course in modeling or complexity, practical guide for interested adults.
Unfortunately, we have not yet been able to find the time to make these happen. If anyone from the user community would like to collaborate on such a venture, please let us know. We would welcome it.
Volunteers have translated the user manual into Chinese and Czech. The translated versions are available from the NetLogo web site.
So far, the NetLogo user interface has been localized in English, Spanish, Chinese, Russian, and Japanese. All five languages are included in the standard download.
We are seeking volunteers to complete and improve these localizations and to translate the NetLogo software and manual into as many other languages as possible. If you’re able to help in this endeavor, please contact us.
Short answer: some of both.
Long answer: NetLogo does include a compiler that generates Java byte code. However, this compiler does not yet support the entire language, so some parts of user code remain interpreted. Note that our compiler generates Java byte code, and Java virtual machines have “just-in-time” compilers that in turn compile Java byte code all the way to native code, so much user code is ultimately translated to native code.
Try looking at the NetLogo Models Library, the NetLogo Modeling Commons, our Community Models page, and our list of references to NetLogo in outside works.
You might also ask the question on the NetLogo Users Group and/or search past messages on the group.
Yes. NetLogo’s pseudorandom number generator and agent scheduling algorithms are deterministic, and NetLogo always uses Java’s “strict math” library, which gives bit-for-bit identical results regardless of platform. But keep the following cautions in mind:
random-seed command to set the random seed in advance, so
that your model will receive the exact same sequence of random numbers every
time. Remember that agentsets are always in random order, so anything you do
with agentsets uses random numbers.every or wait commands in such a way that affects
the outcome of the model, then you may get different results on different
computers, or even on the same computer, since the model may run at a
different speed.For now, yes. NetLogo 3D is included with NetLogo, but it is still a separate application.
Ideally a single unified application would support both 2D and 3D modeling. We would design the 3D world support so it doesn’t get in the way when you are building 2D models. Models built in NetLogo 3D might require changes in order to run in the hypothetical unified application.
No. Neither iOS, nor Android, nor Windows RT supports running Java applications such as NetLogo.
We are working on an alternate implementation of NetLogo on a JavaScript and HTML5 base, instead of Java. It will work on a variety of tablets and phones. We don’t know yet when it will be ready, and we expect that for a long time it will only support a subset of the features in desktop NetLogo. The many person-years of development effort that have gone into the Java version can’t cheaply or easily be replicated on another platform.
For technical details on this new project, go here.
Yes. When you install NetLogo, the folder that is created contains has the version number in its name, so multiple versions can coexist.
On Windows systems, whichever version you installed last will be the version that opens when you double click a model file in Windows Explorer. On Macs, you can control what version opens via “Get Info” in the Finder.
Some of the files in the tarball have long pathnames, too long for the standard
tar format. You must use the GNU version of tar instead (or another program
which understands the GNU tar extensions). On some systems, the GNU version of
tar is available under the name “gnutar”. You can find out if you are already
using the GNU version by typing tar --version and seeing if the output says
“tar (GNU tar)”.
It depends on which platform you are using.
msiexec.exe /i C:\Path\to\NetLogo.msi ALLUSERS=1 ADDLOCAL=Shortcuts :: To install with desktop shortcuts
msiexec.exe /i C:\Path\to\NetLogo.msi ALLUSERS=1 ADDLOCAL=BaseInstall :: To install without desktop shortcuts
We also maintain an advanced installation wiki page which may have additional tips and tricks. We encourage users who have problems with unattended installation or ideas on how it could be improved to email feedback@ccl.northwestern.edu.
Yes. NetLogo runs fine from any file system, including read-only file systems.
Your computer is switching to power saving mode when unplugged. It’s normal for this to reduce speed a little, but unfortunately there is a bug in Java that drastically slows down Swing applications, including NetLogo.
One workaround is to change the power settings on your computer so it doesn’t go into power saving mode when you unplug it. (If you do this, your battery won’t last as long.)
Another workaround is to run NetLogo with an option recommended by Oracle, by editing the NetLogo 6.4.0.vmoptions file, found in the NetLogo directory (under Program Files on your hard drive, unless you installed NetLogo in a different location). Add on a new line:
-Dsun.java2d.ddoffscreen=false
You can see the details of the Java bug and vote for Oracle to fix it here.
Since Mac OS X Lion, Apple have encouraged Mac application developers to bundle Java. NetLogo bundles Java because it allows us to deliver a consistent, convenient experience to our users. Bundling Java allows us to test for compatibility once and avoid any bugs caused by version mismatches or Java configuration incompatibilities.
If users are interested in using Java on their system instead of the version of
Java bundled with NetLogo, they can configure NetLogo to use a different Java
runtime. Please note that this change is done at your own risk. We are
unable to offer support for problems caused by running NetLogo with an alternate
Java Runtime. To change the Java runtime used by NetLogo, open the
NetLogo.cfg file and modify the app.runtime property to
the path of your preferred Java Runtime.
We bundle Bellsoft’s OpenJDK-based Java runtime when using NetLogo on Linux. If you would like to change the version of linux used, you can modify the .cfg files to point to a different version of Java (see How big can my model be? for more information).
In theory, any Java 11 or later runtime will run NetLogo. In practice, some Java implementations aren’t high enough quality. Recent versions of OpenJDK should work; older ones may not. GNU libgcj does not work.
Ubuntu users should consult https://help.ubuntu.com/community/Java.
Windows attempts to protect users from downloading malicious software by maintaining a list of “good” and “malicious” software. The first users to install any NetLogo release will see this warning. Later users may or may not see this warning. Before going any further, ensure you are protected. The CCL can only vouch for NetLogo downloads hosted on the CCL Website. NetLogo can be freely downloaded from the official NetLogo download page. If you obtain NetLogo from anywhere else, you install it at your own risk!
You can continue past the Windows prompt by taking the following steps:
Note in order to see the “More Info” or “Run Anyway” options, you will need to run the installer as an administrator. If you do not see those options, right-click and choose “Run as administrator” and/or change your user account to an administrator account before installing.
We at the CCL are working on solving this problem and hope to free our users of the added installation difficulty soon!
A nearly certain fix is to use a text editor to edit the NetLogo.cfg file, changing 1024m to a smaller number, like 512m. This should permit NetLogo to start, although the lower heap size limit may affect your ability to run models with many agents. See How big can my model be? for information on model size and how to edit the cfg file.
If running with the lower heap size limit is unacceptable, read on.
Some Windows systems have trouble allocating large amounts of contiguous virtual memory. Upgrading to a newer version of Windows may help.
Running Windows in 64-bit mode instead of 32-bit mode may also help. Double check that Windows is actually running in 64-bit mode; see Microsoft’s FAQ page on 64-bit Windows.
Some users have reported problems opening NetLogo 6 on Mac OS Sierra. We’ve been unable to determine a root cause for this problem, but we’re continuing to investigate. We’re looking for assistance from you if you run into this problem. It would be extremely helpful if you could run the following command in the “Terminal” application and send the output in an email to bugs@ccl.northwestern.edu.
xattr -pl com.apple.quarantine /Applications/NetLogo\ 6.4.0/NetLogo\ 6.4.0.app
running it should give you a single line of output (something like
com.apple.quarantine: 01e1;58ac6af2;Firefox;F2E0B1E2-D203-4B05-8DF9-ABA58B52EFEA,
but yours will have different numbers, letters, and words). Please copy and
paste this string into the email you send us.
There is also a partial workaround! Running the following command in the Terminal will enable users to run NetLogo without turning Gatekeeper completely off. The command is:
sudo xattr -dr com.apple.quarantine /Applications/NetLogo\ 6.4.0/NetLogo\ 6.4.0.app
Note that if you plan to run NetLogo 3D or HubNet Client you may also need to re-run that command once for each of those applications. If the workaround was not effective for you, please send us an email and let us know.
Some users on Mac OS with discrete graphics cards experience sudden crashes of NetLogo when switching between integrated and discrete graphics. It’s possible to prevent these crashes by disabling automatic graphics switching in System Preferences.
Some Windows users may also be unable to open NetLogo due to graphics card settings or drivers. If you are unable to open NetLogo on Windows, you might be able to fix this by updating or reinstalling your graphics driver and/or disabling any graphics card utilities. Because NetLogo might be unable to start for a number of reasons, we encourage you to contact us if these steps aren’t effective in resolving the problem.
Yes. The easiest way is to set up your model run or runs as a BehaviorSpace experiment. No additional programming is required. See the BehaviorSpace Guide for details.
Another option is to use our Controlling API. Some light Java programming is required. See the Controlling API Guide for details and sample code.
Only when using BehaviorSpace. BehaviorSpace does parallel runs, one per processor.
For a single model run, only one processor is used.
We are seeking funding to make it possible to split a single model run across multiple processors or multiple computers.
Many of the same comments in the previous answer apply. It is not possible to split a single model run across multiple computers, but you can have each machine in a cluster doing one or more separate, independent model runs, using either BehaviorSpace or our Controlling API. We don’t have automated support for splitting the runs across clusters, so you’ll need to arrange that yourself.
Various users are already using NetLogo on clusters, with a variety of hardware and software. You can seek them out on the NetLogo Users Group.
Yes. NetLogo auto-saves files as you are working on them. The path to the auto-save file depends on whether or not the NetLogo model has been saved.
For NetLogo models which have been saved, a hidden file with the name “.filename.tmp.nlogo” will be created in the same directory as the NetLogo model.
For unsaved NetLogo models, autosave files can be found in your OS-specific java
temporary directory. The files are named according to the following format:
autosave_yyyy-MM-dd.HH_mm_ss.nlogo where the time and date are the time and
date the model was opened. The exact path will depend on your operating system:
/var/folders/68/<30-character-alphanumeric-sequence>/T/. The
30-character-alphanumeric-sequence is unique to each machine.C:\Users\<user>\AppData\Local\Temp,
where <user> is the logged in user./tmp.HubNet discovery provides the ability for HubNet clients running on the same local network as the HubNet server to automatically display the IP address and current activity of the server. This uses IPv4 multicast over a local area network - it won’t identify HubNet servers on the internet or on different networks. Some networks also do not support multicast traffic and it will simply not work on those networks. For HubNet Discovery to work, the server must be broadcasting to the same network that the client is polling for messages. Often, both the client and server are only connected to a single network and there is no need for further configuration.
Since NetLogo 6.0.3, we have tools in place to allow clients and/or servers connected to multiple networks to select the network on which they will broadcast/listen. When running a HubNet server, this is done by selecting the appropriate “broadcast network” via selection dropdown when starting a HubNet server. This preference will be remembered until NetLogo is restarted, so if you end up needing to broadcast on a different network, restart NetLogo. HubNet clients also see a similar dropdown when selecting which activity to join. Unlike HubNet server, clients may change the network on which they listen at any time. HubNet discovery will only work when both client and server are listening/broadcasting on the same network, so some trial and error may be required to figure out a working configuration. Generally speaking, the shared network is the one on which the client and the server have the most similar IP address prefixes. For instance, if the server selects to broadcast on a network where it has IP address 192.168.0.101, a client should prefer listening on a network where it has an IP like 192.167.0.203 over a network where it has an IP like 10.5.0.101. Even when the same network is selected, it is possible that that network may not support IPv4 multicast, in which case discovery will not work and clients must enter IP addresses manually.
Note that the change made in 6.0.3 simply enable selection of the network on which clients and servers broadcast/listen on. The HubNet server still listens on all network connections, so all listed IP addresses given in the server broadcast network selection dropdown are potentially valid for a HubNet client (even a client on a different network) to connect to. Similarly HubNet clients may connect to any HubNet server reachable from their computer.
The only way NetLogo can make your model run faster is by updating the view less frequently. As you move the speed slider to the right, view updates become less and less frequent. Since view updates take time, that means more speed.
However, fewer updates also means that the updates come farther apart. When several seconds pass between updates, it may seem like your model has stopped. It hasn’t. It’s running at full speed. Watch the tick counter! (If your model uses it. If it doesn’t, watch something else, like a plot.)
To get a feel for what’s going on, try moving the slider to the right gradually rather than suddenly. If you find the updates too infrequent at the rightmost position, just don’t push the slider that far.
NetLogo does not have a built-in set of painting tools for painting in the view. But with only a few lines of code, you can add painting capability to your model. To see how it’s done, look at Mouse Example, in the Code Examples section of the Models Library. The same techniques can be used to let the user interact with your model using the mouse in other ways, too.
Another possibility is to create an image in another program and import it using
the import items on the File menu or the import-* primitives.
We have tested NetLogo with models that use hundreds of megabytes of RAM and they work fine. We have reports from NetLogo users that they have run models that required up to 50 gigabytes of RAM to use millions of patches and tens of thousands of agents, and they worked as desired with the proper Java settings. Theoretically the only limit is the RAM available on your system, but you might hit some limits that are inherent in the underlying Java runtime or the operating system (either designed-in limits, or bugs).
The NetLogo engine has no fixed limits on model size. By default NetLogo sets Java to use up to half of your available
system memory. If your model exceeds that memory limit, you’ll get an OutOfMemoryError dialog.
If you are using BehaviorSpace, note that doing runs in parallel will multiply your RAM usage accordingly. Similarly, using LevelSpace with many child models increases RAM usage greatly.
If you want to increase the memory limit Java uses, you can do so using the NetLogo app configuration files.
Each platform contains “.cfg” files containing JVM settings. There is one cfg file for each sub-application (NetLogo, NetLogo 3D, HubNet Client, etc.). Windows also has a cfg file for the NetLogo_Console app; on macOS and Linux the cfg file for NetLogo_Console is just the NetLogo.cfg file. Although the file location varies by platform, the process for changing it is the same. Locate the section of the file that looks like the following:
[JavaOptions]
# there may be one or more lines, leave them unchanged
java-options=-XX:MaxRAMPercentage=50
# there may be one or more lines, leave them unchanged
You can change the percentage number from 50 to whatever you want. Save the file and restart NetLogo for the setting to
take effect. If you need to set an exact amount of memory (as opposed to a percentage), you can also comment out the
java-options=-XX:MaxRAMPercentage=50 line with a # at the start and add a new line with java-options=-Xmx####m.
Replace the ####m with whatever amount of memory you like; using 4096m would limit NetLogo to 4096 megabytes of
memory, or 4 gigabytes.
Platform specific notes follow:
C:\Program Files\NetLogo 6.4.0\app,
unless you are running 32 bit NetLogo on a 64 bit Windows, then it will be
in C:\Program Files (x86)\NetLogo 6.4.0\app./Applications/NetLogo 6.4.0/NetLogo 6.4.0.app/Contents/app/NetLogo 6.4.0.cfg For
NetLogo 3D and the other applications, you will find the file in the
corresponding location for each application package. You can reach the cfg
file by control-clicking the application in the Finder and choosing “Show
Package Contents” from the popup menu.
Please note that depending on your version of Mac OS X, changing the cfg file may break application signing. If this happens, follow Apple’s directions on this page to temporarily allow apps from “Anywhere”, run NetLogo once, then restore the setting to “Mac App Store and Identified Developers”.
NetLogo 6.4.0/lib/app
folder after untarring.By default, Mac builds of NetLogo bundle a 64-bit JVM. Windows and Linux will bundle a 32-bit or 64-bit JVM, depending on which version you have downloaded. It is recommended that you install 64-bit NetLogo on all 64-bit operating systems for best performance.
Yes, many users are using GIS data with NetLogo. The most complete way to do that is with the GIS extension. See the GIS Extension Guide.
A simpler way is to use import-pcolors, but that only works for importing maps
that are images, not maps in other formats.
It is also possible to write NetLogo code that reads GIS data using our file I/O
primitives such as file-open. For example, see the Grand Canyon model in the
Earth Science section of Sample Models.
Here’s some ways to make it run faster without changing the structure of the code:
In many cases, though, if you want your model to run faster, you may need to make some changes to the code. Usually the most obvious opportunity for speedup is that you’re doing too many computations that involve all the turtles or all the patches. Often this can be reduced by reworking the model so that it does less computation per time step. The members of the NetLogo Users Group may be able to help with this.
The profiler extension is useful for identifying which parts of your code are taking the most time.
Unless you are running the exact same strings over and over, using run and
runresult are much slower than running code directly; you should avoid using
these primitives on fresh strings in performance-critical code.
One instance of NetLogo can only have one model open at a time. (Unfortunately, it is unlikely that this will change in a future version, due to the engineering difficulties involved.)
You can have multiple models open by opening multiple instances of NetLogo, though. On Windows and Linux, simply start the application again. On a Mac, you’ll need to duplicate the application (not the whole folder, just the application itself) in the Finder, then open the copy. (The copy takes up only a very small amount of additional disk space.)
No.
On an experimental basis, this is available using the __includes keyword.
This is answered in detail at the end of the Programming Guide.
See the Transition Guide for help.
Any of these ways:
(- x)
-1 * x
0 - x
With the first way, the parentheses are required.
If you have disabled wrapping at the world edges in your model, then the turtle
might be at a world edge and unable to move any further. You can test for this
using can-move?.
Assuming the turtle isn’t hitting a world edge, moving forward 1 is only guaranteed to take a turtle to a new patch if the turtle’s heading is a multiple of 90 (that is, exactly north, south, east, or west).
It’s because the turtle might not be standing in the center of a patch. It might
be near the corner of a patch. For example, suppose your turtle is close to the
southwest corner of a patch and is facing northeast. The length of the patch
diagonal is 1.414… (the square root of two), so fd 1 will leave the turtle
near the northeast corner of the same patch.
If you don’t want to have to think about these issues, one possibility is to write your model in such a way that your turtles always come to rest on patch centers. See next question.
A turtle is on a patch center when its xcor and ycor are integers.
You can move a turtle to the center of its current patch with either of these two equivalent commands:
move-to patch-here
setxy pxcor pycor
But you’ll never need to do that if you never allow turtles off of patch centers in the first place.
The sprout command creates turtles on patch centers. For example:
ask n-of 50 patches [ sprout 1 [ face one-of neighbors4 ] ]
Another way for a turtle to start on a patch center is with a command such as this line of turtle code, which moves it to the center of a random patch:
move-to one-of patches
Once a turtle is on a patch center, as long as its heading always stays an exact multiple of 90 (that is to say, due north, east, south, or west), and as it long as it moves forward or back by integer amounts, it will always land on patch centers.
See Random Grid Walk Example, in the Code Examples section of the Models Library, to see these code snippets in use.
patch-ahead 1 is reporting the same patch my turtle is already standing on. Why?See the answer two answers up. It’s the same issue.
This might not be the meaning of “ahead” you were expecting. With patch-ahead,
you must specify the distance ahead that you want to look. If you want to know
the next patch a turtle would cross into if it moved forward continuously, it is
possible to find that out. See Next Patch Example, in the Code Examples section
of the Models Library.
You can use in-radius to let a turtle see a circular area around it.
Several primitives let the turtle “look” at specific points. The patch-ahead
primitive is useful for letting a turtle see what is directly in front of it. If
you want the turtle to look in another direction besides straight ahead, try
patch-left-and-ahead and patch-right-and-ahead.
If you want the turtle to have a full “cone” of vision, use the in-cone
primitive.
You can also find out the next patch a turtle would cross into if it moved forward continuously. See Next Patch Example, in the Code Examples section of the Models Library.
No. If you want to make marks that agents can sense, use patch colors.
See the “Math” section of the Programming Guide for a discussion of this issue.
random-float 1 might return 0 but will never return 1. What if I want 1 to be included?It really doesn’t matter. Even if 1 were a possible result, it would only come up approximately 1 in 2^64 tries, which means you’d be waiting hundreds of years before it ever came up exactly 1.
Nonetheless, if you are convinced that it really must be possible to get 1, you
can use precision to round your answer to a certain number of decimal places.
For example:
print precision (random-float 1) 10
0.2745173723
(If you use this method, note that 0 and 1 are only half as likely to come up as
other answers. To see why this is so, consider the case where you only keep one
digit after the decimal point. Results between 0 and 0.5 get rounded to 0, but
results between 0.5 and 1.5 get rounded to 1; the latter range is twice as
large. If you want 0, 0.1, 0.2, …, 0.9, and 1 to all be equally likely, an
alternative is to write random 11 / 10; this gives all 11 answers with equal
probability.)
This is caused by a combination of a few things:
turtles are always returned in a random order.So the monitor constantly re-runs its mean [xcor] of turtles reporter, but the turtles agentset gives the turtles in a random order, and so the floating-point inaccuracies for mean will accumulate in a slightly different way each time due to the order differences. The end result is you see very slightly different numbers flashing through the monitor widget while nothing is happening.
You see the same problem doing sum [xcor] of turtles, variance [xcor] of turtles, or standard-deviation [xcor] of turtles - anytime you’re reducing a bunch of floating point numbers from an agentset into a single value. You can also see the problem running your reporter code directly in the command center repeatedly, without a monitor widget at all.
The fixes are straightforward:
mean sort [xcor] of turtles, sum sort [xcor] of turtles, variance sort [xcor] of turtles. If the numbers are in the same order you’ll still have small floating-point inaccuracies, but they’ll be the the same every time so you won’t see the values change. This is probably the best solution, but it can be slow if you have a really large agentset.Decimal places setting of your monitors to a number where you don’t notice the changing values. Since the differences in results should be small, this is usually possible.See One Turtle Per Patch Example, in the Code Examples section of the Models Library.
When a turtle dies, it turns into nobody. nobody is a special value used in
NetLogo used to indicate the absence of a turtle or patch. So for example:
if turtle 0 != nobody [ ... ]
You could also use is-turtle?:
if is-turtle? turtle 0 [ ... ]
Nearly all models should just use lists for this.
The usual motivation for using arrays in other programming languages is that
they provide fast random access (item) and mutation (replace-item). But
NetLogo’s lists, even though they are immutable, now provide near constant time
performance on these operations.
Lists in earlier versions of NetLogo (4.1 and 4.0) were simple singly-linked lists and therefore these operations took linear time. The data structure underlying NetLogo’s lists now is the immutable Vector class from the Scala collections library. It uses 32-wide hash array mapped tries, as implemented by Tiark Rompf, based in part on work by Phil Bagwell and Rich Hickey.
If you are certain you want to use raw, mutable JVM arrays in your model, they are provided by the array extension. See the Arrays & Tables section of the User Manual.
Yes, using the table extension. See the Arrays & Tables section of the User Manual.
The in-radius primitives lets you access circular neighborhoods of any radius.
The neighbors primitive gives you a Moore neighborhood of radius 1, and the
neighbors4 primitive gives you a Von Neumann neighborhood of radius 1.
For Moore or Von Neumann neighborhoods of a larger radius, see Moore & Von Neumann Example in the Code Examples section of the Models Library.
If you want the list in a particular order, use the sort or sort-by
primitives. The Lists section of the Programming Guide explains how to do this.
See also Ask Ordering Example, in the Code Examples section of the Models
Library.
If you want the list in a random order, here’s how:
[self] of <agentset>
Because all operations on agentsets are in random order, the resulting list is in random order.
To convert a list of agents to an agentset, use the turtle-set, patch-set,
or link-set primitives.
To stop a foreach from executing you need to define a separate procedure that contains only the foreach, for example:
to test
foreach [1 2 3] [ i ->
if i = 2 [ stop ]
print i
]
end
This code will only print the number 1. The stop returns from the current
procedure so nothing after the foreach will be executed either. (If the
procedure is a reporter procedure, use report instead of stop.)
If a list contains only literal values, you can write it down just by putting square
brackets around it, like [1 2 3].
If you want your list to contain items that may vary at runtime, the list cannot be written down directly. Instead, you build it using the list primitive.
This is normal when doing multiple runs in parallel. For a discussion of the issue, see the section on parallel runs in the BehaviorSpace Guide section of the User Manual.
Use repeat in your experiment’s go commands, e.g.:
repeat 10 [ go ]
to measure the run after every 10 ticks. Essentially you are making one experiment step equal 10 ticks.
It’s probably because your setup commands or setup procedure are using
clear-all, causing the values set by BehaviorSpace to be cleared.
One possible workaround is to change your experiment’s setup commands to preserve the value of the variable, e.g.:
let old-var1 var1
setup
set var1 old-var1
This works because even clear-all doesn’t clear the values of local variables
made with let
Another possible workaround is to change your model’s setup procedure to use more specific clearing commands to clear only what you want cleared.
NetLogo supports fullscreen exclusive mode. If that is all your device needs then, possibly yes. However, it can be tricky to get it working. We don’t have any such devices so it is difficult for us to make the process easier. If your device needs something else, for example, quadbuffers enabled, the answer is probably no.
org.nlogo.api?You need to add NetLogo.jar to your classpath when compiling. NetLogo.jar is
included with NetLogo.