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• What statistics can be maintained for a set of numerical data without iterating?

  - by Dan Tao

  Update Just for future reference, I'm going to list all of the statistics that I'm aware of that can be maintained in a rolling collection, recalculated as an O(1) operation on every addition/removal (this is really how I should've worded the question from the beginning): Obvious Count Sum Mean Max* Min* Median** Less Obvious Variance Standard Deviation Skewness Kurtosis Mode*** Weighted Average Weighted Moving Average**** OK, so to put it more accurately: these are not "all" of the statistics I'm aware of. They're just the ones that I can remember off the top of my head right now. *Can be recalculated in O(1) for additions only, or for additions and removals if the collection is sorted (but in this case, insertion is not O(1)). Removals potentially incur an O(n) recalculation for non-sorted collections. **Recalculated in O(1) for a sorted, indexed collection only. ***Requires a fairly complex data structure to recalculate in O(1). ****This can certainly be achieved in O(1) for additions and removals when the weights are assigned in a linearly descending fashion. In other scenarios, I'm not sure. Original Question Say I maintain a collection of numerical data -- let's say, just a bunch of numbers. For this data, there are loads of calculated values that might be of interest; one example would be the sum. To get the sum of all this data, I could... Option 1: Iterate through the collection, adding all the values: double sum = 0.0; for (int i = 0; i < values.Count; i++) sum += values[i]; Option 2: Maintain the sum, eliminating the need to ever iterate over the collection just to find the sum: void Add(double value) { values.Add(value); sum += value; } void Remove(double value) { values.Remove(value); sum -= value; } EDIT: To put this question in more relatable terms, let's compare the two options above to a (sort of) real-world situation: Suppose I start listing numbers out loud and ask you to keep them in your head. I start by saying, "11, 16, 13, 12." If you've just been remembering the numbers themselves and nothing more, and then I say, "What's the sum?", you'd have to think to yourself, "OK, what's 11 + 16 + 13 + 12?" before responding, "52." If, on the other hand, you had been keeping track of the sum yourself while I was listing the numbers (i.e., when I said, "11" you thought "11", when I said "16", you thought, "27," and so on), you could answer "52" right away. Then if I say, "OK, now forget the number 16," if you've been keeping track of the sum inside your head you can simply take 16 away from 52 and know that the new sum is 36, rather than taking 16 off the list and them summing up 11 + 13 + 12. So my question is, what other calculations, other than the obvious ones like sum and average, are like this? SECOND EDIT: As an arbitrary example of a statistic that (I'm almost certain) does require iteration -- and therefore cannot be maintained as simply as a sum or average -- consider if I asked you, "how many numbers in this collection are divisible by the min?" Let's say the numbers are 5, 15, 19, 20, 21, 25, and 30. The min of this set is 5, which divides into 5, 15, 20, 25, and 30 (but not 19 or 21), so the answer is 5. Now if I remove 5 from the collection and ask the same question, the answer is now 2, since only 15 and 30 are divisible by the new min of 15; but, as far as I can tell, you cannot know this without going through the collection again. So I think this gets to the heart of my question: if we can divide kinds of statistics into these categories, those that are maintainable (my own term, maybe there's a more official one somewhere) versus those that require iteration to compute any time a collection is changed, what are all the maintainable ones? What I am asking about is not strictly the same as an online algorithm (though I sincerely thank those of you who introduced me to that concept). An online algorithm can begin its work without having even seen all of the input data; the maintainable statistics I am seeking will certainly have seen all the data, they just don't need to reiterate through it over and over again whenever it changes.

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• Haskell's type system treats a numerical value as function?

  - by Long

  After playing around with haskell a bit I stumbled over this function: Prelude Data.Maclaurin> :t ((+) . ($) . (+)) ((+) . ($) . (+)) :: (Num a) => a -> (a -> a) -> a -> a (Data.Maclaurin is exported by the package vector-space.) So it takes a Num, a function, another Num and ultimately returns a Num. What magic makes the following work? Prelude Data.Maclaurin> ((+) . ($) . (+)) 1 2 3 6 2 is obviously not a function (a-a) or did I miss out on something?

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• How can I make a changing numerical value for a taskbar icon in C#?

  - by Waffles

  I'm trying to make a program in C# that monitors the processor time of an application. I'd like to have a feature in this program where the task-bar icon is actually a number representing the processor time (like what coretemp has). How would I go about doing something like this?

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• Javascript: Taking the highest 2 numerical values out of a series of 4 possible values.

  - by Bodhi

  What I'm trying to do is to take the highest two values out of 4 possible variables and add them together, while ignoring the lesser two values. My values will be anywhere between 1 and 5. So, for example, if I have Trait1, Trait2, Trait3 and Trait4 with the following assigned values: 3, 3, 2, 1, the script will pick up the 3 and the 3, but not the 2 and the 1. If I change the values around so that I have 4, 3, 1, 5, the script will pick up the 4 and the 5, but not the 3 and the 1. How would I go about doing this? Thank you in advance.

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• How can I make a numerical value for a taskbar icon in C#?

  - by Waffles

  I'm trying to find a way to display the current processor time of an application to the user via the taskbar when my application is minimized. For reference, I want something like what is implemented in Coretemp, where if you minimize the application, you can still see the temperature of the computer processor cores in the taskbar. Does anyone know of how this is done in C#?

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• How can I left-justify numerical output in fortran?

  - by mishaF

  I am writing some simple output in fortran, but I want whitespace delimiters. If use the following statement, however: format(A20,ES18.8,A12,ES18.8) I get output like this: p001t0000 3.49141273E+01obsgp_oden 1.00000000E+00 I would prefer this: p001t0000 3.49141273E+01 obsgp_oden 1.00000000E+00 I tried using negative values for width (like in Python) but no dice. So, is there a way to left-justify the numbers? Many thanks in advance!

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• In PHP how do a translate a date to numerical format not knowing the format of the string beforehand

  - by stormist

  Examples of the translations I need to do: $stringDate = "November 2009"; $output = "11/09"; $stringDate = "October 1 2010"; $output = "10/01/2010"; $stringDate = "January 2010"; $output = "01/10"; $stringDate = "January 9 2010"; $output = "01/09/2010"; Note that I do not know which format the $stringDate will be in and the lack of commas in the month day year set. Thanks for any help anyone might offer.

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• How to $.extend 2 objects by adding numerical values together from keys with the same name?

  - by muudless

  I currently have 2 obj and using the jquery extend function, however it's overriding value from keys with the same name. How can I add the values together instead? obj1 = {"orange":2,"apple":1, "grape":1} obj2 = {"orange":5,"apple":1, "banana":1} mergedObj = $.extend({}, obj1, obj2); var printObj = typeof JSON != "undefined" ? JSON.stringify : function(obj) { var arr = []; $.each(obj, function(key, val) { var next = key + ": "; next += $.isPlainObject(val) ? printObj(val) : val; arr.push( next ); }); return "{ " + arr.join(", ") + " }"; }; console.log('all together: '+printObj(mergedObj) ); And I get obj1 = {"orange":5,"apple":1, "grape":1, "banana":1} What I need is obj1 = {"orange":7,"apple":2, "grape":1, "banana":1}

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• O&rsquo;Reilly E-Book of the Day 15/Aug/2014 - Advanced Quantitative Finance with C++

  - by TATWORTH

  Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2014/08/15/orsquoreilly-e-book-of-the-day-15aug2014---advanced-quantitative-finance.aspxToday’s half-price book of the Day offer from O’Reilly at http://shop.oreilly.com/product/9781782167228.do?code=MSDEAL is Advanced Quantitative Finance with C++. “This book will introduce you to the key mathematical models used to price financial derivatives, as well as the implementation of main numerical models used to solve them. In particular, equity, currency, interest rates, and credit derivatives are discussed. In the first part of the book, the main mathematical models used in the world of financial derivatives are discussed. Next, the numerical methods used to solve the mathematical models are presented. Finally, both the mathematical models and the numerical methods are used to solve some concrete problems in equity, forex, interest rate, and credit derivatives.”

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• how to change type of value in an php array and sorting it..is it possible ?

  - by justjoe

  hi, i got problem with my code and hopefully someone able to figure it out. The main purpose is to sort array based on its value (then reindex its numerical key). i got this sample of filename : $filename = array("index 198.php", "index 192.php", "index 144.php", "index 2.php", "index 1.php", "index 100.php", "index 111.php"); $alloutput = array(); //all of index in array foreach ($filename as $name) { preg_match('#(\d+)#', $name, $output); // take only the numerical from file name array_shift($output); // cleaned. the last code create duplicate numerical in $output, if (is_array($hasilku)) { $alloutput = array_merge($alloutput, $output); } } //try to check the type of every value in array foreach ($alloutput as $output) { if (is_array($hasil)) { echo "array true </br>"; } elseif (is_int($hasil)) { echo "integer true </br>"; } elseif (is_string($hasil)) { //the numerical taken from filename always resuld "string". echo "string true </br>"; } } the output of this code will be : Array ( [0] = 198 [1] = 192 [2] = 144 [3] = 2 [4] = 1 [5] = 100 [6] = 111 ) i have test every output in array. It's all string (and not numerical), So the question is how to change this string to integer, so i can sort it from the lowest into the highest number ? the main purpose of this code is how to output array where it had been sort from lowest to highest ?

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• Is NAN suitable for communicating that an invalid parameter was involved in a calculation?

  - by Arman

  I am currently working on a numerical processing system that will be deployed in a performance-critical environment. It takes inputs in the form of numerical arrays (these use the eigen library, but for the purpose of this question that's perhaps immaterial), and performs some range of numerical computations (matrix products, concatenations, etc.) to produce outputs. All arrays are allocated statically and their sizes are known at compile time. However, some of the inputs may be invalid. In these exceptional cases, we still want the code to be computed and we still want outputs not "polluted" by invalid values to be used. To give an example, let's take the following trivial example (this is pseudo-code): Matrix a = {1, 2, NAN, 4}; // this is the "input" matrix Scalar b = 2; Matrix output = b * a; // this results in {2, 4, NAN, 8} The idea here is that 2, 4 and 8 are usable values, but the NAN should signal to the receipient of the data that that entry was involved in an operation that involved an invalid value, and should be discarded (this will be detected via a std::isfinite(value) check before the value is used). Is this a sound way of communicating and propagating unusable values, given that performance is critical and heap allocation is not an option (and neither are other resource-consuming constructs such as boost::optional or pointers)? Are there better ways of doing this? At this point I'm quite happy with the current setup but I was hoping to get some fresh ideas or productive criticism of the current implementation.

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• CodePlex Daily Summary for Thursday, February 18, 2010

  CodePlex Daily Summary for Thursday, February 18, 2010New ProjectsASP .NET MVC CMS (Content Management System): Open source Content management system based on ASP.NET MVC platform.AutoFolders: AutoFolders package for Umbraco CMS This package auto creates folder structures for new and existing pages. The folders structures can be date bas...AutoPex: This project combines CCI with Pex by allowing the developer to run Pex on methods based on differences between two assemblies. Canvas VSDOC Intellisense: JavaScript VSDOC documentation for HTML5 Canvas element and 2d Context interface.CSUDH: California State University, Domguiez Hills Game projectsD-AMPS: System for Analysis of Microelectronic and Photonic StructuresDispX: Disease PredictorEmployee Info Starter Kit: This is a starter kit, which includes very simple user requirements, where we can create, read, update and delete (crud) the employee info of a com...Enhanced Discussion Board for SharePoint: Provide later... publishing project to share with Malaysians firstFlowPad: Flowpad is a light, fast and easy to use flow diagram editor. It helps you quickly pour your algorithms from your mind to 'paper'. It is written us...Henge3D Physics Library for XNA: Henge3D is a 3D physics library written in C# for XNA. It is implemented entirely in managed code and is compatible with the XBOX 360.Hybrid Windows Service: Abstracted design pattern for running a windows service interactively. Implemented as a base class to replace ServiceBase it will automatically pro...Image Cropper datatype for Umbraco: Stand alone version of the Image Cropper datatype in Umbraco. Listinator: A social wishlist application done in asp.net MVCMicrosoft Dynamics Ax User Group (AXUG) Code Repository: The goal of this project is to make it easier for customers of Microsoft Dynamics Ax to be able to share relevant source code. Code base should inc...Mobil Trials: Sebuah game sederhana yang dibuat di atas Silverlight 3.0 dengan bantuan Physics Helper 3.0 Demo : http://gameagam.co.cc/default.html Mirror link...NavigateTo Providers: This project is a collection of NavigateTo providers for Visual Studio 2010. NExtLib: NExtLib is a general-purpose extension library for .NET, which adds some useful features and addresses some alleged omissions.Nom - .NET object-mapper: Nom is a light-weight, storage-type agnostic persistence framework which is intended to provide an abstraction over both relational and non-relatio...Numerical Methods on Silverlight: Numerical Methods, Silverlight, Math Parser, Simple, EulerOpenGLViewController for Visual Basic .NET 2008: A single class in pure VB.NET code to create and control an OpenGL window by calling opengl32.dll directly without use of additional wrapper librar...RestaurantMIS: RestaurantMIS is a simple Restaurant management system developed in Visual C# 2008 with Chinese language.SmartKonnect: <project name>A WPF application for windows with shoutcast, twitter, facebook and etc.SSRS Excel file Sheet rename: SSRS wont support renaming excel reports sheet rename. This program support to generate the report and change the excel sheet nameSWENTRIZ.NET: SWENTRIZ.NET allows to build graphics of implicit functions via .NET functionality.TFT: Tropical forecast tracker is a web application. It will measure the error of the National Hurricane Center's forecast as compared to the actual tr...WCF Dynamic Client Proxy: A WCF Dynamic Client Proxy so you don't have to inherit from ClientBase all the time. The proxy also has fault tolerance so you don't have to dispo...Web.Config Role Provider: Stores ASP.NET Roles in web.config. Easy to set up and deploy. Works great for simple websites with authentication. The projects includes support ...WPF Line of Business App: Example WPF patterns for line of business applications. Includes navigation, animation, and visualization.YuBiS Framework: Silverlight and WF based a workflow RAD framework. New ReleasesASP .NET MVC CMS (Content Management System): AtomicCms 1.0: This is the first public release of AtomicCms. To get more information about this content management system, visit website http://atomiccms.com/Blogsprajeesh.Blogspot samples: Designing Modular Smart Clients using CAL: This whitepaper provides architectural guidance for designing and implementing enterprise WPF/ silverlight client applications based on the Composi...DB Ghost Build Tools: 1.0.2: Made a change to the datetime format per dewee.DotNetNuke® Community Edition: 05.02.03: Major HighlightsFixed the issue where LinkClick.aspx links were incorrect for child portals Fixed the issue with the PayPal URL settings. Fixed...Employee Directory webpart for sharepoint 2007 user profiles: Employee Directory Source V2.0: Features: 1. Displays a complete list of all Active Directory profiles imported by the SSP into SharePoint 2007. 2. Displays the following fields ...Enhanced Discussion Board for SharePoint: Alpha Release: Meant for those who attended my presentation. Not cleaned upESPEHA: Espeha 9 PFR: Some small issues fixedFlowPad: FlowPad 0.1: FlowPad 0.1 build. Run it to get fammiliar with major concepts of easy diagramming :)Fluent Ribbon Control Suite: Fluent Ribbon Control Suite BETA2: Fluent Ribbon Control Suite BETA2 Includes: - Fluent.dll (with .pdb and .xml) - Demo Application - Samples - Foundation (Tabs, Groups, Contextu...Henge3D Physics Library for XNA: Henge3D Source (2010-02): This is the initial 2010-02 release.Highlight: Highlight 2.5: This release is primarily a maintenance release of the library and is functionally equivalent to version 2.3 that was released in 2004.Magiq: Magiq 0.3.0: Magiq 0.3.0 contains: Magiq-to-objects: Full support to Linq-to-objects Magiq-to-sql: Full support to Linq-to-sql New features: Plugin model Bu...Microsoft Points Converter: Pre-Alpha ClickOnce Installer v0.03: This release builds on the 0.02 release by adding more thorough validation checks for the amount to convert from as well as adding several currency...Mobil Trials: Mobil Trials Source Code: Sebuah game sederhana yang dibuat di atas Silverlight 3.0 dengan bantuan Physics Helper 3.0 Game ini masih perlu dikembangkan lebih jauh lagi! Si...Numerical Methods on Silverlight: Numerical Methods on Silverlight 1.00: This a new version of Numerical Methods on Silverlight.OAuthLib: OAuthLib (1.5.0.0): Changed point is as next. 7037 Fix spell miss of RequestFactoryMedthodSharePoint Outlook Connector: Version 1.0.1.0: Now it supports simply attaching SharePoint documents feature.Sharpy: Sharpy 1.1 Alpha: This is the second Sharpy release. Only a single change has been made - the foreach function now uses IEnumerable as a source instead of IList. Th...SkinDroidCreator: SkinDroidCreator ALPHA 1: Primera releaseTan solo carga mapas, ya sea de un zip o de un directorio. Para probarlo se pueden cargar temas Metamorph o temas flasheables, ya se...SkyDrive .Net API Client: SkyDrive .Net API Client 0.8.9: SkyDrive .Net API Client assembly version 0.8.9. Changes/improvements: - Added Web Proxy support - Introduced WebDriveInfo - Introduced DownloadUrl...spikes: Salient.Web.Administration 1.0: WebAdmin is simply the built in ASP.NetWebAdministrationFiles application cleaned up with codebehinds to make customization and refactoring possibl...SSRS Excel file Sheet rename: Change SSRS excel file sheet name: Create stored procedure from the attached file in sql server 2005/2008SWENTRIZ.NET: Approach 1: First approachTortoiseSVN Addin for Visual Studio: TortoiseSVN Addin 1.0.4: Visual Studio 2005 support Custom working root bug fixingTotal Commander SkyDrive File System Plugin (.wfx): Total Commander SkyDrive File System Plugin 0.8.4: Total Commander SkyDrive File System Plugin version 0.8.4. Bug fixes: - Upgraded SkyDriveWebClient to version 0.8.9 Please do not forget to expres...UnOfficial AW Wrapper dot Net: UAWW.Net 0.1.5.85 Béta 2: Fixed and Added SomethingVr30 OS: Space Brick Break 1.1: A brick breaker. ADD Level 3, 4, 5Web.Config Role Provider: First release: Three downloads are available: A compiled dll ready to use. The schema to enable intellisense The complete source (zipped)WI Assistant: WI Assistant 2.1: This release improves the work item selection functionality. These selection methods are now supported (some require at least one item selected): ...WI Assistant: WI Assistant 2.2: Improved error handling and fix for linking several times in a row. DISCLAIMER: While I have tested this app on my TFS Server, by downloading and...ZipStorer - A Pure C# Class to Store Files in Zip: ZipStorer 2.30: Added stream-oriented methods Improved support for ePUB & Open Container Format specification (OCF) Automatic switch from Deflate to Store algo...Most Popular ProjectsRawrDotNetNuke® Community EditionASP.NET Ajax LibraryFacebook Developer ToolkitWindows 7 USB/DVD Download ToolWSPBuilder (SharePoint WSP tool)Virtual Router - Wifi Hot Spot for Windows 7 / 2008 R2Json.NETPerformance Analysis of Logs (PAL) ToolQuickGraph, Graph Data Structures And Algorithms for .NetMost Active ProjectsDinnerNow.netRawrSharpyBlogEngine.NETSimple SavantjQuery Library for SharePoint Web ServicesNB_Store - Free DotNetNuke Ecommerce Catalog Modulepatterns & practices – Enterprise LibraryPHPExcelFacebook Developer Toolkit

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• Storing and analyzing rock climbing difficulty

  - by Zonedabone

  I'm working on a WordPress plugin to manage rock climbing data, and I need to think of a way to store rock climbing grades from all of the different systems in a unified way. There are many different systems, all of which have some numerical system. A comparison of all the systems: http://en.wikipedia.org/wiki/Grade_(climbing)#Comparison_tables Is there some unified way that I can store and analyze these, or do I just need to assign numbers to them all and call it a day? My current plan is to save the score type and then assign each score a numerical value, which I can then use to compare and graph them.

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• simple PHP integer conversion

  - by Ygam

  convert this: $300 to this : 300 can't do it with intval() or (int) typecasting if the non-numerical character is suffixed (300$), both works and returns 300 if it is prefixed it returns 0 the non-numerical character can be anything other than the "$"(i.e. "askldjflksdjflsd") Please help

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• Removing characters from a alphanumeric field SQL

  - by LS

  Im moving data from one table to another using insert into. in the select bit need to transfer from column with characters and numerical in to another with only the numerical. The original column is in varchar format. original column - ABC100 XYZ:200 DD2000 Wanted column 100 200 2000 Cant write a function because cant have a function in side select statement when inserting

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• Bracketing algorithm when root finding. Single root in "quadratic" function

  - by Ander Biguri

  I am trying to implement a root finding algorithm. I am using the hybrid Newton-Raphson algorithm found in numerical recipes that works pretty nicely. But I have a problem in bracketing the root. While implementing the root finding algorithm I realised that in several cases my functions have 1 real root and all the other imaginary (several of them, usually 6 or 9). The only root I am interested is in the real one so the problem is not there. The thing is that the function approaches the root like a cubic function, touching with the point the y=0 axis... Newton-Rapson method needs some brackets of different sign and all the bracketing methods I found don't work for this specific case. What can I do? It is pretty important to find that root in my program... EDIT: more problems: sometimes due to reaaaaaally small numerical errors, say a variation of 1e-6 in some value the "cubic" function does NOT have that real root, it is just imaginary with a neglectable imaginary part... (checked with matlab) EDIT 2: Much more information about the problem. Ok, I need root finding algorithm. Info I have: The root I need to find is between [0-1] , if there are more roots outside that part I am not interested in them. The root is real, there may be imaginary roots, but I don't want them. Probably all the rest of the roots will be imaginary The root may be double in that point, but I think that actually doesn't mater in numerical analysis problems I need to use the root finding algorithm several times during the overall calculations, but the function will always be a polynomial In one of the particular cases of the root finding, my polynomial will be similar to a quadratic function that touches Y=0 with the point. Example of a real case: The coefficient may not be 100% precise and that really slight imprecision may make the function not to touch the Y=0 axis. I cannot solve for this specific case because in other cases it may be that the polynomial is pretty normal and doesn't make any "strange" thing. The method I am actually using is NewtonRaphson hybrid, where if the derivative is really small it makes a bisection instead of NewRaph (found in numerical recipes). Matlab's answer to the function on the image: roots: 0.853553390593276 + 0.353553390593278i 0.853553390593276 - 0.353553390593278i 0.146446609406726 + 0.353553390593273i 0.146446609406726 - 0.353553390593273i 0.499999999999996 + 0.000000040142134i 0.499999999999996 - 0.000000040142134i The function is a real example I prepared where I know that the answer I want is 0.5 Note: I still haven't check completely some of the answers I you people have give me (Thank you!), I am just trying to give al the information I already have to complete the question.

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• Generics that Restricts the Types to Int, Double, long

  - by Ngu Soon Hui

  Is it possible to constraint a method so that it receives only int, double, long or other numerical types that has the usual numerical operations ( such as +,-,*,/) defined?

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• C++ Expression Templates

  - by yCalleecharan

  Hi, I currently use C for numerical computations. I've heard that using C++ Expression Templates is better for scientific computing. What are C++ Expression Templates in simple terms? Are there books around that discuss numerical methods/computations using C++ Expression Templates? In what way, C++ Expression Templates are better than using pure C? Thanks a lot

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• Too Many Files In Debian Linux Folder?

  - by Dave Potts

  I've been using an external USB drive on a Debian server for backup. The drive is formatted as NTFS and mounted with ntsfmount. This was working fine, but I was filling up a directory with lots of files. Eventually the backup failed. When I then tried to look at the directory using ls it reported: ls: reading directory .: Numerical result out of range Looking in syslog, I also saw this: Sep 23 07:35:31 tosh ntfsmount[28040]: Failed to read index block: Numerical result out of range. Is this simply that I've reached the upper limit of number of files in a directory? If so, is there any way to extend the number of allowed files?

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• Easiest method of creating multiple Word documents with incremental number?

  - by DakotaDusty

  I need to create about 80 Word documents that are identical except for a numerical identifier in the document. The identifier is the same as the document filename, eg. the document named "SN-100.doc" must have the string "SN-100" inside the document text. Each unique document will reside in a folder location given by its unique numerical identifier.For example, the file directory hierarchy will look something like this: /SN001/SN-1.doc /SN002/SN-2.doc . . . /SN080/SN-80.doc What is the easiest and fastest method of doing this?

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• How to filter a mysql database with user input on a website and then spit the filtered table back to the website? [migrated]

  - by Luke

  I've been researching this on google for literally 3 weeks, racking my brain and still not quite finding anything. I can't believe this is so elusive. (I'm a complete beginner so if my terminology sounds stupid then that's why.) I have a database in mysql/phpmyadmin on my web host. I'm trying to create a front end that will allow a user to specify criteria for querying the database in a way that they don't have to know sql, basically just combo boxes and checkboxes on a form. Then have this form 'submit' a query to the database, and show the filtered tables. This is how the SQL looks in Microsoft Access: PARAMETERS TEXTINPUT1 Text ( 255 ), NUMBERINPUT1 IEEEDouble; // pops up a list of parameters for the user to input SELECT DISTINCT Table1.Column1, Table1.Column2, Table1.Column3,* // selects only the unique rows in these three columns FROM Table1 // the table where this query is happening WHERE (((Table1.Column1) Like TEXTINPUT1] AND ((Table1.Column2)<=[NUMBERINPUT1] AND ((Table1.Column3)>=[NUMBERINPUT1])); // the criteria for the filter, it's comparing the user input parameters to the data in the rows and only selecting matches according to the equal sign, or greater than + equal sign, or less than + equal sign What I don't get: WHAT IN THE WORLD AM I SUPPOSED TO USE (that isn't totally hard)!? I've tried google fusion tables - doesn't filter right with numerical data or empty cells in rows, can't relate tables I've tried DataTables.net, can't filter right with numerical data and can't use SQL without a bunch of indepth knowledge, not even sure it can if you have that.. I've looked into using jQuery with google spreadsheets, doesn't work at all either I have no idea how I'm supposed to build a front end with my database. Every place that looks promising (like zohocreator) is asking for money, and is far too simplified to be able to do the LIKE criteria or SELECT DISTINCT stuff.

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• How do I choose the scaling factor of a 3D game world?

  - by concept3d

  I am making a 3D tank game prototype with some physics simulation, am using C++. One of the decisions I need to make is the scale of the game world in relation to reality. For example, I could consider 1 in-game unit of measurement to correspond to 1 meter in reality. This feels intuitive, but I feel like I might be missing something. I can think of the following as potential problems: 3D modelling program compatibility. (?) Numerical accuracy. (Does this matter?) Especially at large scales, how games like Battlefield have huge maps: How don't they lose numerical accuracy if they use 1:1 mapping with real world scale, since floating point representation tend to lose more precision with larger numbers (e.g. with ray casting, physics simulation)? Gameplay. I don't want the movement of units to feel slow or fast while using almost real world values like -9.8 m/s^2 for gravity. (This might be subjective.) Is it ok to scale up/down imported assets or it's best fit with a world with its original scale? Rendering performance. Are large meshes with the same vertex count slower to render? I'm wondering if I should split this into multiple questions...

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• Javascript: Machine Constants Applicable?

  - by DavidB2013

  I write numerical routines for students of science and engineering (although they are freely available for use by anybody else as well) and am wondering how to properly use machine constants in a JavaScript program, or if they are even applicable. For example, say I am writing a program in C++ that numerically computes the roots of the following equation: exp(-0.7x) + sin(3x) - 1.2x + 0.3546 = 0 A root-finding routine should be able to compute roots to within the machine epsilon. In C++, this value is specified by the language: DBL_EPSILON. C++ also specifies the smallest and largest values that can be held by a float or double variable. However, how does this convert to JavaScript? Since a Javascript program runs in a web browser, and I don't know what kind of computer will run the program, and JavaScript does not have corresponding predefined values for these quantities, how can I implement my own version of these constants so that my programs compute results to as much accuracy as allowed on the computer running the web browser? My first draft is to simply copy over the literal constants from C++: FLT_MIN: 1.17549435082229e-038 FLT_MAX: 3.40282346638529e+038 DBL_EPSILON: 2.2204460492503131e-16 I am also willing to write small code blocks that could compute these values for each machine on which the program is run. That way, a supercomputer might compute results to a higher accuracy than an old, low-level, PC. BUT, I don't know if such a routine would actually reach the computer, in which case, I would be wasting my time. Anybody here know how to compute and use (in Javascript) values that correspond to machine constants in a compiled language? Is it worth my time to write small programs in Javascript that compute DBL_EPSILON, FLT_MIN, FLT_MIN, etc. for use in numerical routines? Or am I better off simply assigning literal constants that come straight from C++ on a standard Windows PC?

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• Correct permutation cycle for Verhoeff algorithm

  - by James

  Hello, I'm implementing the Verhoeff algorithm for a check digit scheme, but there seems to be some disagreement in web sources as to which permutation cycle should form the basis of the permutation table. Wikipedia uses: (36)(01589427) while apparently, Numerical Recipies uses a different cycle and this book uses: (0)(14)(23)(56789), quoted from a 1990 article by Winters. It also notes that Verhoeff used the one Wikipedia quotes. Now, my number theory is a little rusty, but the Wikipedia cycle clearly will repeat after the 8th power, while the book one will take 10, despite it saying that s^8=s. Table 2.14(b) has other errors in the 2-cycles, so this is dubious anyway. Unfortunately, I don't have copies of the original articles (and am too tight to pay/disgusted that 40-year old knowledge is still being held to ransom by publishers), nor a copy of Numerical Recipes to check (and am loath to install their paranoia-induced copy protection plug-in to view online). So does any one know which is correct? Are they both correct?

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• How do I get the cell value from a formula in Excel using VBA?

  - by Simon

  I have a formula in a range of cells in a worksheet which evaluate to numerical values. How do I get the numerical values in VBA from a range passed into a function? Let's say the first 10 rows of column A in a worksheet contain rand() and I am passing that as an argument to my function... public Function X(data as Range) as double for c in data.Cells c.Value 'This is always Empty c.Value2 'This is always Empty c.Formula 'This contains RAND() next end Function I call the function from a cell... =X(a1:a10) How do I get at the cell value, e.g. 0.62933645? Excel 2003, VB6

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