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Search found 196 results on 8 pages for 'maths'.

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• Computationally simple Pseudo-Gaussian Distribution with varying mean and standard deviation?

  - by mstksg

  This picture from wikipedia has a nice example of the sort of functions I'd ideally like to generate http://en.wikipedia.org/wiki/File:Normal_Distribution_PDF.svg Right now I'm using the Irwin-Hall Distribution, which is more or less a Polynomial approximation of the Gaussian distribution...basically, you use uniform random number generator and iterate it x times, and take the average. The more iterations, the more like a Gaussian Distribution it is. It's pretty nice; however I'd like to be able to have one where I can vary the mean. For example, let's say I wanted a number between the range 0 and 10, but around 7. Like, the mean (if I repeated this function multiple times) would turn out to be 7, but the actual range is 0-10. Is there one I should look up, or should I work on doing some fancy maths with standard Gaussian Distributions?

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• C# Expression Tree Simple Arithmetic

  - by Richard Adnams

  Hello, I've been trying to figure out how to achieve some simple maths using the Expression class. What I'm trying to do is this (1 + 10 * 15) When I try to do this via Expression.Add and Expression.Constant but the result I get is this ((1 + 10) * 15) Which is not right as it evaluates the 1 + 10 first instead of 10 * 15. Is there a way to combine Expression.Add/Multiply etc.. without it creating the brackets? I assume there is but I just can't find where or how! The test code I have is this var v1 = Expression.Constant(1, typeof(int)); var v2 = Expression.Constant(10, typeof(int)); var v3 = Expression.Constant(15, typeof(int)); var a1 = Expression.Add(v1, v2); var m2 = Expression.Multiply(a1, v3); Thanks for your time, Richard.

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• Developing ebooks- software?

  - by Mark Mayo

  I've written a few documents for friends or blogs on software testing, job hunting and android development. I've been toying with the idea of producing some programming-related ebooks. However, developing these in Word or OpenOffice seems too amateurish compared to some of the fantastically produced books out there. I'm proficient in LaTeX but have never seen it used to produce ... 'marketable' works - just technical papers, maths, etc - which is great for code but not for distribution. Has anyone seen any good (preferably free / open source) tool or software for developing/compiling professional-looking marketable ebooks (probably to .pdf or .exe format - but I can take care of that part if need be)? And more importantly, ones that are easy to use to format any code samples or snippets that I may choose to include. Much appreciated.

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• Render only the segment/area of a circle that intersects the main circle

  - by Greenhouse Gases

  I absolutely love maths (or 'math' as most of you would say!) but I haven't done it to a level where I know the answer to this problem. I have a main circle which could have a centre point at any x and y on a display. Other circles will move around the display at will but at any given call to a render method I want to render not only those circles that intersect the main circle, but also only render the segment of that circle that is visible inside the main circle. An analogy would be a shadow cast on a real life object, and I only want to draw the part of that object that is 'illuminated'. I want to do this preferably in Java, but if you have a raw formula that would be appreciated. I wonder how one might draw the shape and fill it in Java, I'm sure there must be some variation on a polyline with arcs or something? Many thanks

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• Download estimator control using JavaScript and Ajax

  - by Anil Namde

  I would like to implement the download estimator using the JavaScript and the Ajax. I have gone trough Google to find the existing implementations for the download estimator and i found most of the time asking user bandwidth and then calculating the number is strategy. It good approach and there is hardly anything on reliable to get the estimated time right. What i would like to try is use Ajax to request file size 100KB - 200 KB and do the maths get the number and update the display. Now this is surrounded with so many questions like network, number of packets formed, proxies etc ? These all factors are sufficient to turn down the approach. But THIS IS HOW I HAVE TO DO THIS ? Now i would like here inputs from you all to make it better (as good discussion)? what all can be added to this ? Can we get to know bandwidth user using without asking ?

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• Clojure: Testing every value from map operation for truth

  - by Ralph

  How can I test that every value in the collection returned by map is true? I am using the following: (defn test [f coll] (every? #(identity %) (map f coll))) with the anonymous function #(identity %), but I was wondering if there is a better way. I cannot use (apply and ...) because and is a macro. UPDATE: BTW, I am making my way through The Haskell Road to Logic, Maths, and Programming, by Kees Doets and Jan can Eijck, but doing the exercises in Clojure. It's a very interesting book.

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• I like to learn computer science and programming, but i have no understanding.

  - by Josiah

  Hi all, I like to learn computer science and programming, but i don't know where and how to start. For the past two months, i have been researching on types of programming, i found my interest in desktop programming, and also found this subjects (discrete maths, logic, algorithms, data structures, artificial intelligence, simulation) said to be a most known (subjects). Well as a beginner, i have no understanding on what type of language or books that can cover all these subjects, or even how to write any code. Secondly, am as young as you can guess and i need a language to start with that will be easy for me to understand, and books to read. Thank you.

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• Unique keys for Sphinx along three vectors instead of two

  - by Brendon Muir

  I'm trying to implement thinking-sphinx across multiple 'sites' hosted under a single rails application. I'm working with the developer of thinking-sphinx to sort through the finer details and am making good progress, but I need help with a maths problem: Usually the formula for making a unique ID in a thinking-sphinx search index is to take the id, multiply it by the total number of models that are searchable, and add the number of the currently indexed model: id * total_models + current_model This works well, but now I also through an entity_id into the mix, so there are three vextors for making this ID unique. Could someone help me figure out the equation to gaurantee that the id's will never collide using these three variables: id, total_models, total_entities The entity ID is an integer. I thought of: id * (total_models + total_entities) + (current_model + current_entity) but that results in collisions. Any help would be greatly appreciated :)

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• What's a better choice for SQL-backed number crunching - Ruby 1.9, Python 2, Python 3, or PHP 5.3?

  - by Ivan

  Crterias of 'better': fast im math and simple (little of fields, many records) db transactions, convenient to develop/read/extend, flexible, connectible. The task is to use a common web development scripting language to process and calculate long time series and multidimensional surfaces (mostly selectint/inserting sets of floats and dong maths with rhem). The choice is Ruby 1.9, Python 2, Python 3, PHP 5.3, Perl 5.12, JavaScript (node.js). All the data is to be stored in a relational database (due to its heavily multidimensional nature), all the communication with outer world is to be done by means of web services.

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• Mathematics for AI/Machine learning ?

  - by Ankur Gupta

  I intend to build a simple recommendation systems for fun. I read a little on the net and figured being good at math would enable on to build a good recommendation system. My math skills are not good. I am willing to put considerable efforts and time in learning maths. Can you please tell me what mathematics topics should I cover? Also if any of you folks can point me to some online material to learn from it would be great. I am aware of MIT OCW, book like collective intelligence. Math Topics to cover and from where to read would really help.

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• Ruby implementation of conversion between Latitude/Longitude and OS National Grid Reference point?

  - by Harry Wood

  For converting between Latitude/Longitude and UK's Ordnance Survey National Grid eastings and northings, this seems to be the most popular explanation and reference implementation in JavaScript: http://www.movable-type.co.uk/scripts/latlong-gridref.html The web is littered with other implementations in different languages. Making the conversion via PostGIS queries is another alternative. ...but did anyone implement this maths in ruby? OSGridToLatLong is the direction I'm looking for just at this moment, but I would have thought a library for converting in both directions must surely be available in a gem somewhere. I'm just not searching for the right thing.

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• Putting $$s in the middle of an `equation` environment: why doesn't Latex complain?

  - by Charles Stewart

  I was surprised that the Latex code from a recent question didn't throw up any errors, and even more surprised on further investigation, that Crowley's explanation seems to be true. My intuition about the \begin{equation} ... \end{equation} code is clearly off, what's really going on? Consider this, slightly adapted code: \begin{equation} 1: e^{i\pi}+1=0 $$ 2: B\"ob $$ 3: e=mc^2 \end{equation} This seems to prove that Crowley's explanation of such code, namely that "What that code says to LaTeX is begin equation, end it, begin it again, typeset definition of tangens and end the equation" is right: lines 1&3 can only be typeset in maths mode, line 2 only in text mode. Shouldn't Latex see that the \end{equation} is ending a display math that wasn't started by the \begin{equation}?

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• How do I determine the dimensions of a .NET listview at runtime?

  - by Dave

  I have a form with a split container and each panel has a list view and some buttons. I wanted to make sure that the header and at least two rows are visible in a listview. I originally determined the values for panel1MinSize & panel2MinSize by fine tuning the values visually (on my XP development machine). This approach was fine until I tested my app on Windows Vista - the basic dimensions of the listview are different and the listview is too small. To overcome this I believe I need to determine the listview dimensions at runtime and do some maths to set the panel min size but I can't see how to do this. Is this the right approach or is there an easier way?

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• Select Columns Only if String length is greater than 2

  - by Zee-pro

  Similar Question may be asked but I am unable to find anything that fits my needs. How can I select only columns where string length is greater than 2 This is how much has done yet. SELECT * FROM Table1 WHERE (Table1.ID = @ID) Or something like WHERE (Table1.ID = @ID) AND (LEN(*) > 2) Thank for all of your help I have a Table, in which I have 35 columns and a User ID column, now I want to select and display information from only those columns which have 2 string. I Like to Select only columns which have 2 string and the defined ID by User not the Whole Row !! I hope I am making sense. Table Desired Result DI 35 Lesson 4 Maths Lesson 9 ICT Lesson 12 English

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• What is the need for normalizing a vector?

  - by Rashed Hassan

  Trying to understand vectors a bit more. What is the need for normalizing a vector? If I have a vector, N = (x, y, z) What do you actually get when you normalize it - I get the idea you have to divide x/|N| y/|N| & z/|N|. My question is, why do we do this thing, I mean what do we get out of this equation? What is the meaning or 'inside' purpose of doing this. A bit of a maths question, I apologize, but I am really not clear in this topic.

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• Stored Procedure or calculations via IQueryable?

  - by Shawn Mclean

  This is a question that is based on choosing performance over design practices. If I have a method that will be executed many times a second; public static IQueryable<IPerson> InRadius(this IQueryable<IPerson> query, Coordinate center, double radius) { return (from u in query where CallHeavyMathFormula(u, center, radius) select u); } This extension method for IQueryable generates a SQL that does some heavy maths calculation (Cosine, Sine, etc). This would mean the application sends 1-2KB of sql to the server per call. I've heard of placing all application logic, in your application. I also would like to change to a database such as azure or one of those scalable databases in the future. How do I handle something like this? Should I leave it as it is now or write stored procedures? How do applications like twitter or facebook do it?

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• Looking for ideas on automatically arranging a set of objects (furniture) in a virtual room in AS3

  - by raf

  First of all, I don't want to visually arrange 3D models dragging them with the mouse, all I want is: Given a room of certain dimensions (L,W,H) and given a set of elements like beds, chairs, etc (with L,W,H dimensions, of course) I want to automatically arrange those elements to take advantage of the space as much as I can. So I want to be able to put as much furniture as I can in a given room. At the end I need to represent the arranged items visually, inside the room. My first thought was to use an array of items and sorting it with array.sortOn(["l","w","h"] Array.NUMERIC) and then define a gap between the objects and make the maths to put the objects one next to another, etc. but that isn't a good approach because some items may be placed on top of another ones (boxes of the same size, boxes on top of tables, etc). I really don't have experience on 3D programming, that's why I'm asking for help. Thanks in advance.

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• python parallel computing: split keyspace to give each node a range to work on

  - by MatToufoutu

  My question is rather complicated for me to explain, as i'm not really good at maths, but i'll try to be as clear as possible. I'm trying to code a cluster in python, which will generate words given a charset (i.e. with lowercase: aaaa, aaab, aaac, ..., zzzz) and make various operations on them. I'm searching how to calculate, given the charset and the number of nodes, what range each node should work on (i.e.: node1: aaaa-azzz, node2: baaa-czzz, node3: daaa-ezzz, ...). Is it possible to make an algorithm that could compute this, and if it is, how could i implement this in python? I really don't know how to do that, so any help would be much appreciated

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• Python recursive program

  - by mathboy

  I'm relatively newcomer on programming as I'm educated a mathematician and have no experience on Python. I would like to know how to solve this problem in Python which appeared as I was studying one maths problem on my own: Program asks a positive integer m. If m is of the form 2^n-1 it returns T(m)=n*2^{n-1}. Otherwise it writes m to the form 2^n+x, where -1 < x < 2^n, and returns T(m)=T(2^n-1)+x+1+T(x). Finally it outputs the answer.

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• VBA long overflow

  - by HK_CH

  Hi I am trying to do some maths with my VBA excel (prime factorization) and I am hitting the limit of the long data type (runtime error 6 Overflow). Is there any way to get around this and still stay within VBA? (I am aware that the obvious one would be to use another more appropriate programming language) Thanks for help in advance! Thank you, it works in so far that I am able to get the big numbers into the variables now. However when I try to apply the MOD function (bignumber MOD 2 for example) it still fails with error message runtime error 6 Overflow.

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• Datagrid binding 2 datafiled under one column along with an image?

  - by prince23

  hi, here i am performing nested grid operation where in my first datagrid . have name,age,address once user clicks the row we will be showing another grid that is with data Subject name and Score untill here the functionality works fine . 1:now the Question is that i should be displaying an image along with score in the same column( how can i achive this one) 2:Depending on the score i need to show an image( binding different image based on score) 1 :that is if score is 20 show ( ~images/image1.jpg) 2 :that is if score is 40 show ( ~images/image2.jpg) 3 :that is if score is 20 show (~images/ image3.jpg) output [ in a grid format] subject score science 45 image3 maths 50 image2 Computer 60 image1 general 78 image1 how do we solve this issue . any idea how to go ahead. please let me know. hope my question is clear thanks in advance prince

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• Basic C++ code for multiplication of 2 matrix or vectors (C++ beginner)

  - by Ice

  I am a new C++ user and I am also doing a major in Maths so thought I would try implement a simple calculator. I got some code off the internet and now I just need help to multiply elements of 2 matrices or vectors. Matrixf multiply(Matrixf const& left, Matrixf const& right) { // error check if (left.ncols() != right.nrows()) { throw std::runtime_error("Unable to multiply: matrix dimensions not agree."); } /* I have all the other part of the code for matrix*/ /** Now I am not sure how to implement multiplication of vector or matrix.**/ Matrixf ret(1, 1); return ret; }

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• "Inlining" (kind of) functions at runtime in C

  - by fortran

  Hi, I was thinking about a typical problem that is very JIT-able, but hard to approach with raw C. The scenario is setting up a series of function pointers that are going to be "composed" (as in maths function composition) once at runtime and then called lots and lots of times. Doing it the obvious way involves many virtual calls, that are expensive, and if there are enough nested functions to fill the CPU branch prediction table completely, then the performance with drop considerably. In a language like Lisp, I could probably process the code and substitute the "virtual" call by the actual contents of the functions and then call compile to have an optimized version, but that seems very hacky and error prone to do in C, and using C is a requirement for this problem ;-) So, do you know if there's a standard, portable and safe way to achieve this in C? Cheers

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• Select lowest nested selector when clicked

  - by rikAtee

  I would like to click $('.sub-menu') selector and return the lowerst nested item that was clicked, rather than the highest. e.g., when I click "enlish", "root" is returned becasue "english" is a child of "root". I want "english" returned when I select "english". <div ID="browse_container"> <div class="sub-menu">Root <div class="sub-menu">English</div> <div class="sub-menu">Maths <div class="sub-menu">Year 1</div> <div class="sub-menu">Year 2</div> </div> <div class="sub-menu">? Science</div> </div> </div> my script is simply: $('.sub-menu, #root').on('click', function(event){ alert($(this).text()) });

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• WPF binding: Doing a temperature converter app

  - by Bob

  Hi there, I'm doing a little app that basically has 2 text boxes. You'll enter Fahrenheit into TextBoxA and Celsius into TextBoxB. As the text changes in TextBoxA I want the equivalent Celsius value to be displayed in TextBoxB and vice versa. I can come up with a solution pretty easy for this but i'm trying to be a little clever. Is there a way to do it all in Xaml except for a Convert class that does the maths? So basically I want the TextChanged event of one textBox to pass in it's value into a Converter class that is evaluated and sent to the other TextBox and visa versa. Anyone know how I can achieve this ... and if it's possible at all?

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