Thanks for reading.
I want to implement a Baysian Network using the Matlab's BNT toolbox.The thing is, I can't find "easy" examples, since it's the first time I have to deal with BN.
Can you propose some possible applications, (with not many nodes) please ^^ ?
Have a look at Tom Mitchell's "Machine Learning" book, which covers the subject starting with small, simple examples. I suspect there are many course slides you could access online which also give simple examples.
I think it helps to start with higher level tools to get a feel for how to construct networks before constructing them in code. Having a UI also allows you to play with the network and get a feel for the way the networks behave (propagation, explaining away, etc).
For example have a look at the free Genie (http://genie.sis.pitt.edu) and its samples, and/or the 50 node limited Hugin-Lite (http://www.hugin.com/productsservices/demo/hugin-lite) with it's sample networks. You can then check your BNT implementations to make sure they verify against the software packages.
Edit: I forgot to mention Netica which is another BN/Influence diagram software package which I think has the biggest selection of examples http://www.norsys.com/netlibrary/index.htm.
Related
I am a beginner to this Anylogic software. I have tried some ways to make my model work for milkrun in last mile delivery. I used statecharts and modeling library in constructing the logic, but have not successfully cracked the logic. I have looked into anylogic cloud, it helped in learning bits and pieces. But could not find a model in this case. Any ideas or example models would be much helpful to realize my model.
Thank you:)
There are lots of supply chain-type models in the examples that ship with the tool. You can also check out YouTube for in-depth tutorials, here is one that could be relevant to your case.
I'm trying to come up with the largest possible group of friends that would theoretically get along with each other, i.e., each person in the group should know at least 50% of the other people in the group.
I'm trying to come up with an algorithm for this that doesn't take ridiculously long; Facebook's API/cross-server talk is pretty slow as is.
I was thinking I could start with the friend that has the most mutual friends with me first, and then add people to the group one by one. But who would I choose next?
Just interested in the theory, no code is necessary.
Edit: When I said "theory", what I really meant what's the next logical step in plain english :) I was hoping I could code this up in an afternoon, but I guess this is a bit more complicated than I anticipated, and I'm not sure I want to spend weeks delving into heavy graph theory. Nevertheless, maybe someone else will find this interesting.
MIT did some work on social graphing a while back. Although it used mobile phone data, the clustering algorithms and other systems should still apply, even though they are constructed using different inputs and criteria.
There is more MIT chatter about social graphing going on at the moment. Definitely the place to look for technical pointers on this kind of thing.
Whilst the problem of graph enumeration from a given node to it's edges is NP complete for most useful problems ... the application of the graph traversal and the wealth of information might help you make this more efficient:
For any node (profile) N, you could data-scrape using Google or something to find associated edges out. This means that you can harness a cache of the pages and Googles search technology to mitigate having to traverse the edges yourself.
Social profiles contain tons of meta-data. Developing a statistical analysis method for working out the likelyhood of A knowing B without a direct path might be useful. Afterall friends have a) similar locations and b) similar interests
Other data, seemingly irrelevant can provide a means for locating people likely to know eachother and then you can double check the edges. Things such as chatter on boards about a band or gig, or people mentioning "cat fight" when Kate smacked Mary in the mouth.
The data just needs looking at in the right way, in the same way MIT looked at geographical statistics to determine relationships through phones.
Good Luck
There is an Algorithm called SCAN-Algorithm with some precalculations the algorithm can cluster a network in a good speed.
You can find informations about the algorithm here: SCAN: A Structural Clustering Algorithm for Networks
This is more "broad", but see if it helps to get ideas.
What qualities made it so great, and what made it stand out compared to the not-so-great specs that you've had to deal with? Or, if you've never worked with a good functional spec before, what sort of things would you expect in a great spec?
Sorry this is obviously subjective but I'm creating a functional spec (not my first) and it just occurred to me that I may get some good ideas from the bright folks on SO!
The Project Aardvark specs from Joel on Software are the best I've come across so far. Each screen is defined very well, with pictures. The main features of the software are described, as well as some technical details.
Sadly the specs I've received personally aren't that brilliant. Usually they are just a bulleted list of features they expect from each section of the system, and they expect you to work out all the details. Which is fine, I guess. However, I'm writing a game design document for an RPG game I'm working on as a personal project, and I think the specs I'm writing are very well written. I've divided the game into Sections such as
Characters
Weapons & Armor
Levels
Map
Physics
and so on, and described each section in terms of gameplay as well as some technical details. Its very easy to work through.
I also highly recommend reading the Painless Functional Specs Series from Joel on Software for anyone interested in writing better specs.
IMHO, a key quality should be that the functional spec specifies the "what" in great detail but not the "how". That way, the requestor (marketing?) gets the look & feel and feature set that they want, but the implementation is left to those who know it best -- the developers.
Obviously, the specification should be complete, consistent and comprehensible. IMO it should also be well-organized, in that it keeps all requirements for a specific part of the product together. I've more than once read specifications where requirements for some module were scattered throughout the whole document, e.g. the general description is in chapter 4, but additional requirements can found in clauses in chapters 2, 5, 7 and appendix B. To work with such a specification, I first have to create a cross-reference map of requirements to modules.
A good spec should state what the application is supposed to do, in a clear manner.
This seems obvious, but the stuff I usually get is often very vague. Apparently it's not very easy for people to express what they want on paper, IF they even know what they want.
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I'm really interested in Artificial Neural Networks, but I'm looking for a place to start.
What resources are out there and what is a good starting project?
First of all, give up any notions that artificial neural networks have anything to do with the brain but for a passing similarity to networks of biological neurons. Learning biology won't help you effectively apply neural networks; learning linear algebra, calculus, and probability theory will. You should at the very least make yourself familiar with the idea of basic differentiation of functions, the chain rule, partial derivatives (the gradient, the Jacobian and the Hessian), and understanding matrix multiplication and diagonalization.
Really what you are doing when you train a network is optimizing a large, multidimensional function (minimizing your error measure with respect to each of the weights in the network), and so an investigation of techniques for nonlinear numerical optimization may prove instructive. This is a widely studied problem with a large base of literature outside of neural networks, and there are plenty of lecture notes in numerical optimization available on the web. To start, most people use simple gradient descent, but this can be much slower and less effective than more nuanced methods like
Once you've got the basic ideas down you can start to experiment with different "squashing" functions in your hidden layer, adding various kinds of regularization, and various tweaks to make learning go faster. See this paper for a comprehensive list of "best practices".
One of the best books on the subject is Chris Bishop's Neural Networks for Pattern Recognition. It's fairly old by this stage but is still an excellent resource, and you can often find used copies online for about $30. The neural network chapter in his newer book, Pattern Recognition and Machine Learning, is also quite comprehensive. For a particularly good implementation-centric tutorial, see this one on CodeProject.com which implements a clever sort of network called a convolutional network, which constrains connectivity in such a way as to make it very good at learning to classify visual patterns.
Support vector machines and other kernel methods have become quite popular because you can apply them without knowing what the hell you're doing and often get acceptable results. Neural networks, on the other hand, are huge optimization problems which require careful tuning, although they're still preferable for lots of problems, particularly large scale problems in domains like computer vision.
I'd highly recommend this excellent series by Anoop Madhusudanan on Code Project.
He takes you through the fundamentals to understanding how they work in an easy to understand way and shows you how to use his brainnet library to create your own.
Here are some example of Neural Net programming.
http://www.codeproject.com/KB/recipes/neural_dot_net.aspx
you can start reading here:
http://web.archive.org/web/20071025010456/http://www.geocities.com/CapeCanaveral/Lab/3765/neural.html
I for my part have visited a course about it and worked through some literature.
Neural Networks are kind of declasse these days. Support vector machines and kernel methods are better for more classes of problems then backpropagation. Neural networks and genetic algorithms capture the imagination of people who don't know much about modern machine learning but they are not state of the art.
If you want to learn more about AI and machine learning, I recommend reading Peter Norvig's Artificial Intelligence: A Modern Approach. It's a broad survey of AI and lots of modern technology. It goes over the history and older techniques too, and will give you a more complete grounding in the basics of AI and machine Learning.
Neural networks are pretty easy, though. Especially if you use a genetic algorithm to determine the weights, rather then proper backpropagation.
I second dwf's recommendation of Neural Networks for Pattern Recognition by Chris Bishop. Although, it's perhaps not a starter text. Norvig or an online tutorial (with code in Matlab!) would probably be a gentler introduction.
A good starter project would be OCR (Optical Character Recognition). You can scan in pages of text and feed each character through the network in order to perform classification. (You would have to train the network first of course!).
Raul Rojas' book is a a very good start (it's also free). Also, Haykin's book 3rd edition, although of large volume, is very well explained.
I can recommend where not to start. I bought An Introduction to Neural Networks by Kevin Gurney which has good reviews on Amazon and claims to be a "highly accessible introduction to one of the most important topics in cognitive and computer science". Personally, I would not recommend this book as a start. I can comprehend only about 10% of it, but maybe it's just me (English is not my native language). I'm going to look into other options from this thread.
http://www.ai-junkie.com/ann/evolved/nnt1.html is a clear introduction to multi-layers perceptron, although it does not describe the backpropagation algorithm
you can also have a look at generation5.org which provides a lot of articles about AI in general and has some great texts about neural network
If you don't mind spending money, The Handbook of Brain Theory and Neural Networks is very good. It contains 287 articles covering research in many disciplines. It starts with an introduction and theory and then highlights paths through the articles to best cover your interests.
As for a first project, Kohonen maps are interesting for categorization: find hidden relationships in your music collection, build a smart robot, or solve the Netflix prize.
I think a good starting point would always be Wikipedia. There you'll find some usefull links to documentations and projects which use neural nets, too.
Two books that where used during my study:
Introductional course: An introduction to Neural Computing by Igor Aleksander and Helen Morton.
Advanced course: Neurocomputing by Robert Hecht-Nielsen
I found Fausett's Fundamentals of Neural Networks a straightforward and easy-to-get-into introductory textbook.
I found the textbook "Computational Intelligence" to be incredibly helpful.
Programming Collective Intelligence discusses this in the context of Search and Ranking algorithms. Also, in the code available here (in ch.4), the concepts discussed in the book are illustrated in a Python example.
I agree with the other people who said that studying biology is not a good starting point... because theres a lot of irrelevant info in biology. You do not need to understand how a neuron works to recreate its functionality - you only need to simulate its actions. I recomend "How To Create A Mind" by Ray Kurzweil - it goes into the aspect of biology that is relevant for computational models, (creating a simualted neuron by combining several inputs and firing once a threshhold is reached) but ignores the irrelvant stuff like how the neuron actually adds thouse inputs togeather. (You will just use + and an inequality to compare to a threshold, for example)
I should also point out that the book isn't really about 'creating a mind' - it only focuses on heirarchical pattern recognition / the neocortex. The general theme has been talked about since the 1980s I beleive, so there are plenty of older books that probably contain slightly dated forms of the same information. I have read older documents stating that the vision system, for example, is a multi layered pattern recognizer. He contends that this applies to the entire neocortex. Also, take his 'predictions' with a grain of salt - his hardware estimates are probably pretty accurate, but i think he underestimates how complicated simple tasks can be (ex: driving a car). Granted, he has seen a lot of progress (and been part of some of it) but i still think he is over optimistic. There is a big difference between an AI car being able to drive a mile successfully 90% of the time, when compared to the 99.9+% that a human can do. I don't expect any AI to be truly out driving me for atleast 20 years... (I don't count BMWs track cars that need to be 'trained' on the actual course, as they aren't really playing the same game)
If you already have a basic idea of what AI is and how it can be modeled, you may be better off skipping to something more technical.
If you want to do quickly learn about applications of some neural network concepts on a real simulator, there is a great online book (now wiki) called 'Computational Cognitive Neuroscience' at http://grey.colorado.edu/CompCogNeuro/index.php/CCNBook/Main
The book is used at schools as a textbook, and takes you through lots of different brain areas, from individual neurons all the way to higher-order executive functioning.
In addition, each section is augmented with homework 'projects' that are already down for you. Just download, follow the steps, and simulate everything that the chapter talked about. The software they use, Emergent, is a little finnicky but incredibly robust: its the product of more than 10 years of work I believe.
I went through it in an undergrad class this past semester, and it was great. Walks you through everything step by step
I will be entering my third year of university in my next academic year, once I've finished my placement year as a web developer, and I would like to hear some opinions on the two modules in the Title.
I'm interested in both, however I want to pick one that will be relevant to my career and that I can apply to systems I develop.
I'm doing an Internet Computing degree, it covers web development, networking, database work and programming. Though I have had myself set on becoming a web developer I'm not so sure about that any more so am trying not to limit myself to that area of development.
I know HCI would help me as a web developer, but do you think it's worth it? Do you think Neural Network knowledge could help me realistically in a system I write in the future?
Thanks.
EDIT:
I thought it would be useful to follow-up with what I decided to do and how it's worked out.
I picked Artificial Neural Networks over HCI, and I've really enjoyed it. Having a peek into cognitive science and machine learning has ignited my interest for the subject area, and I will be hoping to take on a postgraduate project a few years from now when I can afford it.
I have got a job which I am starting after my final exams (which are in a few days) and I was indeed asked if I had done a module in HCI or similar. It didn't seem to matter, as it isn't a front-end developer position!
I would recommend taking the module if you have it as an option, as well as any module consisting of biological computation, it will open up more doors should you want to go onto postgraduate research in the future.
The worthiness depends on three factors:
How familiar are you with the topic already?
How good is the course/class you want to take?
What are your interested in more?
Especially for HCI, there is a broad range of "common sense" information you would also easily obtain from reading a good book or a wider range of articles about it also published on the internet. On the other hand, there indeed exist many deeper insights mostly obtained by Psychology studies. If the course is done right, you can indeed learn a lot about the topic and the real considerations to use for developing an interface.
For Neural Networks, one has to say that this is a typical hype topic. It would be mainly interesting in what application domain the course wants to deal with neural networks. You can be quite sure that you won't program or use any neural networks for web development. On the other hand, if the course is done right, this could be a good opportunity for you to broaden your knowledge. Especially, deepening your understanding about the theory of computer science. This highly depends on how the course is laid out, though.
HCI is a topic which helps your career as a web developer, but only if you feel incompetent in that topic (then it is a must) or it is done very well. Neural Networks is a topic which has more potential of being really interesting hardcore computer science stuff, where you indeed learn a better understanding about something. If you are interested in NN, you should not pass the opportunity to get an education which is not narrowly concentrated on the domain of web development -- and, after all, perhaps find more interest in other stuff (it is always good to know other directions you would perhaps like to go into for the future).
Neural networks sound cool until you read the fine print:
In modern software implementations of
artificial neural networks the
approach inspired by biology has more
or less been abandoned for a more
practical approach based on statistics
and signal processing.
This is something that has mystified me for years. Here you have an amazingly complex and powerful control system (real-world biological neural networks), and an academic discipline that appears to be about modeling these systems in software but that has in reality abandoned that activity.
If you're doing web development, your time is probably better spent in the HCI course.
Go with what interests you the most. The HCI stuff will be much easier to pick up later as needed, you'll likely never get another chance to learn about neural networks!
For prospective employers (at least the good ones!) you need to show a passion and excitement about what you do. I'd sooner hire someone who can enthusiastically talk about neural networks than someone who has an extra credit in HCI.
Unless you want to do the research end of the world, ie, get a Masters/PhD, go HCI.
I studied Neural Computation at University when I studied AI. I now run my own company. The number of times since I studied that I have used my NN skills equals zero. I'm glad I did it, as it was quite fascinating, but I would have found HCI much more useful from the position I'm at now. I think that you'd pick up a lot more insight from an HCI course relevant to the software industry, but if you think you experience should be more on the esoteric/almost arty side of development, go for NN.
Which sounds like more fun? Or, equivalently, which will you work harder at? Pick that one.
Did two courses in NN and some other AI-courses - its fun to poke round with that stuff and I actually managed to implement the stuff in some of the things I've done like face-recognition, and it's useful in some other areas to if you wanna plot your lab data etc. I have never used the NN:s in my web development career though I am sure it could be used for something however what it all really boils down to is to find a client or employee willing pay for it when you can just take the straight path. So I would rather read book about it if I wasn't that hardcore about it.
Fundamental Neural Networks doesn't take to much knowledge in math, and was what I used in my first course.
as a programmer to be you need the knowledge of neural network. if parallel processing is the way to go in hardware then future programmers must be knowledgable in neural network. don't forget that NN works better with noise or imprecise data but other systems may not. Note that most data we use for analysis are sample data which is a fraction of the whole and you could imagine if some in the sample are way off. so you need knowledge of NN if you want to last in computer programming field.