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  • Interpolation of scattered data: What could I do?

    - by Simon
    Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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  • Plain-English tutorial on artificial neural networks?

    - by Stuart
    I've Googled, StackOverflowed, everything, and I cannot seem to find a tutorial I can understand. I understand the concept of genetic algorithms, and how to implement them, (Though I haven't tried) but I cannot grasp the concept of neural networks. I know vaguely how they work... And that's about it. Could someone direct me to a tutorial that could help someone who has not even graduated middle school yet? Sure, I'm several years ahead of the majority of people my grade, but I don't understand summation, (which I apparently need if I don't want a simple binary output) vectors, and other things that I apparently should know. Is there a simple, bare-bones tutorial for neural networks? After I learn the basics, I'll proceed to more difficult ones. Preferably, they would be in Java. Thanks!

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  • Functional data structures in C++

    - by drg
    Does anyone know of a C++ data structure library providing functional (a.k.a. immutable, or "persistent" in the FP sense) equivalents of the familiar STL structures? By "functional" I mean that the objects themselves are immutable, while modifications to those objects return new objects sharing the same internals as the parent object where appropriate. Ideally, such a library would resemble STL, and would work well with Boost.Phoenix (caveat- I haven't actually used Phoenix, but as far as I can tell it provides many algorithms but no data structures, unless a lazily-computed change to an existing data structure counts - does it?)

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  • Which OOD approach should I take?

    - by Sorush Rabiee
    According to Niklaus Wirth, Algorithms + Data Structures = Programs. So I use this as a start point to object-oriented modeling and inheritance design: in a way that I separate the 'Objects' from 'Operations'. then look for patterns and inheritance hierarchy. But now after practice I guess it's not a good idea for every modeling problem, because sometimes it's not effective. (I mean there is no possibility of developing (or is very hard to develop) codes of Turing-Completed languages based on this paradigm.) What is your viewpoint for designing an OOD structure as an experienced programmer?

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  • Evenly select N elems from array

    - by ninuhadida
    Hi, I need to evenly select n elements from an array. I guess the best way to explain is by example. say I have: array [0,1,2,3,4] and I need to select 3 numbers.. 0,3,4. of course, if the array length <= n, I just need to return the whole array. I'm pretty sure there's a defined algorithm for this, been trying to search, and I took a look at Introduction to algorithms but couldn't find anything that met my needs (probably overlooked it) The problem I'm having is that I can't figure out a way to scale this up to any array [ p..q ], selecting N evenly elements. note: I can't just select the even elements from the example above.. A couple other examples; array[0,1,2,3,4,5,6], 3 elements ; I need to get 0,3,6 array[0,1,2,3,4,5], 3 elements ; I need to get 0, either 2 or 3, and 5

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  • Discrete and Continuous Classifier on Sparse Data

    - by Chris S
    I'm trying to classify an example, which contains discrete and continuous features. Also, the example represents sparse data, so even though the system may have been trained on 100 features, the example may only have 12. What would be the best classifier algorithm to use to accomplish this? I've been looking at Bayes, Maxent, Decision Tree, and KNN, but I'm not sure any fit the bill exactly. The biggest sticking point I've found is that most implementations don't support sparse data sets and both discrete and continuous features. Can anyone recommend an algorithm and implementation (preferably in Python) that fits these criteria? Libraries I've looked at so far include: Orange (Mostly academic. Implementations not terribly efficient or practical.) NLTK (Also academic, although has a good Maxent implementation, but doesn't handle continuous features.) Weka (Still researching this. Seems to support a broad range of algorithms, but has poor documentation, so it's unclear what each implementation supports.)

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  • What should every programmer know about security ?

    - by M.H
    I am an IT student and I am now in the 3rd year in university,until now we are studing a lot of subjects related to computer in general (Programming,Algorithms,Computer architecture,maths....etc). But there is a whole world called security we are very far from it ,I mean here security in general(Computers Security,Interner Security,Networks Security,hacking,cracking...etc). I am very sure that nobody can learn every thing about security but sure there is a "minimum" knowledge every programmer or IT student should know about it and my question is what is this minimum knowledge ? can you suggest some E-books or courses or any thing can help to start with this road ?

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  • Storing old previous year data in Rails?

    - by Millisami
    Hi, I'm developing an app which has massive data entries. Its like Campaign which has attrs like rate_per_sq_feet, start_date, end_date. i.e it will have max date of around 30 days. Once the campaign is finished, its done and another starts. Now I'm confused that how to store those campaigns as reports so that its not accessed regurlarly. What I mean is to store in such a way that it will act like report on later years to come? Its something like fiscal year on accounts where the previous year reports are stored with all the calculations done so that when retrieved later, all the algorithms and calculations shouldn't be performed. Something like frozen data??

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  • Java - Collections.binarySearch with PriorityQueue?

    - by msr
    Hello, Can I use Collections.binarySearch() method to search elements in a PriorityQueue? Otherwise, how can I apply search algorithms to a PriorityQueue? I have this (class Evento implements Comparable): public class PriorityQueueCAP extends PriorityQueue<Evento>{ // (...) public void removeEventos(Evento evento){ Collections.binarySearch(this, evento); // ERROR! } } And I got this error: "The method binarySearch(List, T) in the type Collections is not applicable for the arguments (PriorityQueueCAP, Evento)" Why? Thanks in advance!

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  • Good "Modelling & Simulation" book recommendations for programmers?

    - by Harry
    I'm a programmer, and have completely forgotten all the advanced engineering Math I studied ~20 years ago at school. I now have an urgent need to learn about Modelling and Simulation. Though the present context is Disease Modelling, I'm not sure if there's such a thing as 'general' modelling and simulation... with concepts / techniques / algorithms that could be used in just about any domain (and not just limited to biology, finance, trade, economic, weather, etc.) Would you have any recommendations that are easy to read by a semi-Math-literate programmer? Basically, I cannot afford to drown myself in too much Math and theory behind M & S, hence this post. Tia...

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  • Text editing best practices (with tags, etc.)

    - by Ron
    Hi there, I want to create a text field with some text, that is styled with tags. Think of MS Word, some ext is bold, some is a headline, etc. The tags that style the text are not visible to the user, he just sees the text in bold. How do I preserve these tags? I mean when I backspace over the closing bold-tag, for example, how do I preserve that and prevent that the rest of the text is now bold until the end? I guess this is a pretty basic question for experiences programmers. Are there any algorithms or best practices? This problem surely has been solved before, any pointers? (If this is of any concern, I develop for the iPhone OS and the text field will be a UITextView, but my question is more general I guess.) Thanks in advance!

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  • FIPS-compliant encryption in .NET 2.0

    - by Odrade
    We have a .NET 2.0 application that uses the RijindaelManaged class to encrypt some sensitive data. This was fine until we ran into some machines that require the use of FIPS-compliant algorithms. We'd like to switch to AesCryptoServiceProvider, but most of our target machines haven't upgraded past .NET 2.0. Requiring an upgrade is out of the question. After all, upgrades are scary! Is there any way we could use AesCryptoServiceProvider in a .NET 2.0 application? Since 3.5 uses the 2.0 CLR, I was hoping there might be a way to build the needed libraries into the app. Failing that, could someone point me to a reference on the native API that's wrapped by AesCryptoServiceProvider?

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  • How to perform FST (Finite State Transducer) composition

    - by Tasbeer
    Consider the following FSTs : T1 0 1 a : b 0 2 b : b 2 3 b : b 0 0 a : a 1 3 b : a T2 0 1 b : a 1 2 b : a 1 1 a : d 1 2 a : c How do I perform the composition operation on these two FSTs (i.e. T1 o T2) I saw some algorithms but couldn't understand much. If anyone could explain it in a easy way it would be a major help. Please note that this is NOT a homework. The example is taken from the lecture slides where the solution is given but I couldn't figure out how to get to it.

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  • Math: How to sum each row of a matrix

    - by macek
    I have a 1x8 matrix of students where each student is a 4x1 matrix of scores. Something like: SCORES S [62, 91, 74, 14] T [59, 7 , 59, 21] U [44, 9 , 69, 6 ] D [4 , 32, 28, 53] E [78, 99, 53, 83] N [48, 86, 89, 60] T [56, 71, 15, 80] S [47, 67, 79, 40] Main question: Using sigma notation, or some other mathematical function, how can I get a 1x8 matrix where each student's scores are summed? # expected result TOTAL OF SCORES S [241] T [146] U [128] D [117] E [313] N [283] T [222] S [233] Sub question. To get the average, I will multiply the matrix by 1/4. Would there be a quicker way to get the final result? AVERAGE SCORE S [60.25] T [36.50] U [32.00] D [29.25] E [78.25] N [70.75] T [55.50] S [58.25] Note: I'm not looking for programming-related algorithms here. I want to know if it is possible to represent this with pure mathematical functions alone.

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  • how to run this qt script? (newbie question)

    - by GB_J
    I have a qt script(barchart.qs) that creates a graph for me. I don't know how i can incorporate(ie show the graph) in my qt mainwindow. Can some one please help me look at the code and what its outputs are? I tried engine.evaluate, but i do not know what is the QScriptValue i'm getting in return. Thanks sooo much. This is the script: BarChart.prototype = new QWidget; BarChart.prototype.suffix = ""; function BarChart(parent) { QWidget.call(this, parent); } // find the maximum value and widest (pixel-wise) label and suffix BarChart.prototype.showEvent = function(event) { var fm = new QFontMetrics(this); this.margin = 20; this.titleHeight = fm.height(); this.barHeight = 1.5 * fm.height(); this.barSpacing = 0.6 * fm.height(); this.maxValue = this.suffixWidth = this.labelWidth = 0; var count = 0; for (d in this.data) { this.labelWidth = Math.max(this.labelWidth, fm.width(d)); this.maxValue = Math.max(this.maxValue, this.data[d]); this.suffixWidth = Math.max(this.suffixWidth, fm.width(String(this.data[d]) + " " + this.suffix)); count++; } this.startHue = 15; this.hueDelta = 360 / count; this.size = new QSize(640, this.titleHeight + 2 * this.margin + (this.barHeight + this.barSpacing) * count); } BarChart.prototype.paintEvent = function(event) { var p = new QPainter; p.begin(this); // background and title p.fillRect(this.rect, new QBrush(new QColor(255, 255, 255))); p.drawText(0, 0, this.width, this.margin + this.titleHeight, Qt.AlignCenter, this.windowTitle, 0); var ofs = this.labelWidth + this.margin; var ww = this.width - this.suffixWidth - ofs - 2 * this.margin; var hue = this.startHue; var y = 0; p.translate(this.margin, this.titleHeight + 1.5 * this.margin); for (d in this.data) { // label on the left side p.setPen(new QColor(Qt.black)); p.drawText(0, y, this.labelWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignRight, d, 0); // the colored bar var gradient = new QLinearGradient(new QPoint(ofs, y), new QPoint(ofs, y + this.barHeight)); gradient.setColorAt(0, QColor.fromHsv(hue, 255, 240)); gradient.setColorAt(1, QColor.fromHsv(hue, 255, 92)); p.setBrush(new QBrush(gradient)); p.setPen(new QColor(96, 96, 96)); var bw = this.data[d] * ww / this.maxValue; p.drawRect(ofs, y, bw, this.barHeight); // extra text at the end of the bar var text = new String(this.data[d] + " " + this.suffix); p.setPen(new QColor(Qt.black)); p.drawText(ofs + bw + this.margin/2, y, this.suffixWidth, this.barHeight, Qt.AlignVCenter + Qt.AlignLeft, text, 0); // for the next bar y += (this.barHeight + this.barSpacing); hue += this.hueDelta; if (hue >= 360) hue -= 360; } p.end(); } BarChart.prototype.wheelEvent = function(event) { this.startHue += event.delta() / 8 / 5; if (this.startHue = 360) this.startHue -= 360; if (this.startHue < 0) this.startHue += 360; this.update(); event.ignore(); } BarChart.prototype.mousePressEvent = function(event) { var fname = QFileDialog.getSaveFileName(this, "Save", ".", "*.png", 0, 0); if (fname.length > 0) { var img = new QImage(this.size, QImage.Format_ARGB32_Premultiplied); this.render(img); img.save(new QFile(fname)); } } var chart = new BarChart; chart.windowTitle = "Monthly"; chart.suffix = "reports"; chart.data = { "September" : 45, "October" : 60, "November" : 56, "December" : 0 }; chart.show(); QCoreApplication.exec();

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  • big O notation algorithm

    - by niggersak
    Use big-O notation to classify the traditional grade school algorithms for addition and multiplication. That is, if asked to add two numbers each having N digits, how many individual additions must be performed? If asked to multiply two N-digit numbers, how many individual multiplications are required? . Suppose f is a function that returns the result of reversing the string of symbols given as its input, and g is a function that returns the concatenation of the two strings given as its input. If x is the string hrwa, what is returned by g(f(x),x)? Explain your answer - don't just provide the result!

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  • Comparison of music data

    - by Christian P.
    Hey I am looking for theory, algorithms and similar for how to compare music. More specifically, I am looking into how to dupecheck music tracks that have different bitrates or perhaps slightly different variations (radio vs album version), but otherwise sound the same. Use cases for this include services such as Grooveshark, Youtube, etc. where they get a lot of duplicate tracks. I am also interested in text comparisons (Britney Spers vs Britney Spears, how far they deviate, etc.) although this is secondary and I already have some sources to go on in this area. I am mostly interested in codec-agnostic comparison techniques and algoritms (assuming a "raw" stream), but codec-specific resources are appreciated. I am aware of projects such as musicbrainz.org, but have not investigated it further, and would be interested if such projects could be of help in this endeavor.

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  • Is it a good idea to create an STL iterator which is noncopyable?

    - by BillyONeal
    Most of the time, STL iterators are CopyConstructable, because several STL algorithms require this to improve performance, such as std::sort. However, I've been working on a pet project to wrap the FindXFile API (previously asked about), but the problem is it's impossible to implement a copyable iterator around this API. A find handle cannot be duplicated by any means -- DuplicateHandle specifically forbids passing handles to it. And if you just maintain a reference count to the find handle, then a single increment by any copy results in an increment of all copies -- clearly that is not what a copy constructed iterator is supposed to do. Since I can't satisfy the traditional copy constructible requirement for iterators here, is it even worth trying to create an "STL style" iterator? On one hand, creating some other enumeration method is going to not fall into normal STL conventions, but on the other, following STL conventions are going to confuse users of this iterator if they try to CopyConstruct it later. Which is the lesser of two evils?

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  • Java Memory Management

    - by Tara Singh
    I am designing a client-server chat application in Java. This is a secure application where the messages are exchanged using cryptographic algorithms. I have one server and it can support many clients. My problem is that when one client logs on the server it works fine, but when another user logs into the system, the server starts giving me bad padding exceptions for the encrypted text. I am not able to figure out the problem, according to my logic, when new connection request to server is made, the server creates a thread for listening to the client. Is it possible that once the instance of thread class is created, it does all the processing correctly for the first client, but not for the second client because the variables in server listener thread class already have some previous value, and thus the encrypted text is not decrypted properly? Please advise how I can make this process more robust so that the number of clients does not affect how well the server functions.

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  • C++: building iterator from bits

    - by gruszczy
    I have a bitmap and would like to return an iterator of positions of set bits. Right now I just walk the whole bitmap and if bit is set, then I provide next position. I believe this could be done more effectively: for example build statically array for each combination of bits in single byte and return vector of positions. This can't be done for a whole int, because array would be too big. But maybe there are some better solutions? Do you know any smart algorithms for this?

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  • In LaTeX prefer figures on text-heavy pages.

    - by bjarkef
    Hi LaTeX seems to have a preference for placing figures together on a page, and placing surrounding text on a separate page. Can I somehow change that balance a bit, as I prefer figures to break up the text to avoid too black text-heavy pages. Example: \section{Some section} [Half a page of text] \begin{figure} [...] \caption{Figure text 1} \end{figure} [Half a page of text] \begin{figure} [...] \caption{Figure text 2} \end{figure} [More text] So what LaTeX usually does is to stack the two half pages of text on a single page, and the figures on the following page. I believe this really gives a bad balance, and bores the reader. So can I change that somehow? I know about postfixing the \begin{figure} with [ht!], but often it does not really matter. I would like to configure the balancing algorithms in LaTeX to naturally prefer pages with combined figures and text.

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  • What's the best general programming book to review basic development concepts?

    - by Charles S.
    I'm looking for for a programming book that reviews basic concepts like implementing linked lists, stacks, queues, hash tables, tree traversals, search algorithms, etc. etc. Basically, I'm looking for a review of everything I learned in college but have forgotten. I prefer something written in the last few years that includes at least a decent amount of code in object-oriented languages. This is to study for job interview questions but I already have the "solving interview questions" books. I'm looking for something with a little more depth and explanation. Any good recommendations?

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  • How to do a natural sort on an NSArray?

    - by Cory Imdieke
    I've got an array of objects, and I need them sorted by their "title" key. It's currently working, though it's using an ASCII sort instead of a natural sort. The titles are filenames, so they look like this: file1 file2 file3 ... file10 file11 file12 I'm getting, as you would expect: file1 file10 file11 file12 file2 file3 ... Does anyone know if there is a way built-in to the NSArray sorting functionality to get this natural sorting as opposed to the alphabetical sort? I found some generic algorithms, but I was hoping for something built-in...

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  • Efficient heaps in purely functional languages

    - by Kim
    As an exercise in Haskell, I'm trying to implement heapsort. The heap is usually implemented as an array in imperative languages, but this would be hugely inefficient in purely functional languages. So I've looked at binary heaps, but everything I found so far describes them from an imperative viewpoint and the algorithms presented are hard to translate to a functional setting. How to efficiently implement a heap in a purely functional language such as Haskell? Edit: By efficient I mean it should still be in O(n*log n), but it doesn't have to beat a C program. Also, I'd like to use purely functional programming. What else would be the point of doing it in Haskell?

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  • Interpreting Search Results

    - by Simon
    Hi all, I am tasked with writing a program that, given a search term and the HTML source of a page representing search results of some unknown search engine (it can really be anything, a blog, a shop, Google, eBay, ...), needs to build a data structure of the results containing "what's in the results": a title for earch result, the "details" link, the position within the results etc. It is not known whether the results page contains any of the data at all, and whether there are any search results. The goal is to feed the data structure into another program that extracts meaning. What I am looking for is not BeautifulSoup or a RegExp but rather some clever ideas or algorithms on how to interpret the HTML source. What do I do to find out what part of the page constitutes a single result item? How do I filter the markup noise to extract the important bits? What would you do? Pointers to fields of research covering what I try to to are aly greatly appreciated. Thanks, Simon

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