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  • PowerPivot, Stocks Exchange and the Moving Average

    - by AlbertoFerrari
    In this post I want to analyze a data model that perform some basic computations over stocks and uses one of the most commonly needed formula there (and in many other business scenarios): a moving average over a specified period in time. Moving averages can be very easily modeled in PowerPivot, but there is the need for some care and, in this post, I try to provide a solid background on how to compute moving averages. In general, a moving average over period T1..T2 is the average of all the values...(read more)

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  • Hashing 3D position into 2D position

    - by notabene
    I am doing volumetric raycasting and curently working on depth jitter. I have 3D position on ray and want to sample 2D noise texture to jitter the depth. Function for converting (or hashing) 3D position to 2D have to produce absolutely different numbers for a little changes (especialy because i am sampling in texture space so sample values differs very very little) and have to be "shader-wise" - so forget about branches, cycles etc. I'm looking forward for yours nice and fast solutions.

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  • Can a 10-bit monitor connection preserve all tones in 8-bit sRGB gradients on a wide-gamut monitor?

    - by hjb981
    This question is about color management and the use of a higher color depth, 10 bits per channel (30 bits in total, resulting in 1.07 billion colors, or 1024 shades of gray, sometimes referred to as "deep color") compared to the standard of 8 bits per channel (24 bits in total, 16.7 million colors, 256 shades of gray, sometimes referred to as "true color"). Do not confuse with "32 bit color", which usually refers to standard 8 bit color with an extra channel ("alpha channel") for transparency (used to achieve effects like semi-transparent windows etc). The following can be assumed to be in place: 1: A wide-gamut monitor that supports 10-bit input. Further, it can be assumed that the monitor has been calibrated to its native gamut and that an ICC color profile has been created. 2: A graphics card that supports 10-bit output (and is connected to the monitor via DisplayPort). 3: Drivers for the graphics card that support 10-bit output. If applications that support 10-bit output and color profiles would be used, I would expect them to display images that were saved using different color spaces correctly. For example, both an sRGB and an adobeRGB image should be displayed correctly. If an sRGB image was saved using 8 bits per channel (almost always the case), then the 10-bit signal path would ensure that no tonal gradients were lost in the conversion from the sRGB of the image to the native color space of the monitor. For example: If the image contains a pixel that is pure red in 8 bits (255,0,0), the corresponding value in 10 bits would be (1023,0,0). However, since the monitor has a larger color space than sRGB, sending the signal (1023,0,0) to the monitor would result in a red that was too saturated. Therefore, according to the ICC color profile, the signal would be transformed into a different value with less red saturation, for example (987,0,0). Since there are still plenty of levels left between 0 and 987, all 256 values (0-255) for red in the sRGB color space of the file could be uniquely mapped to color-corrected 10-bit values in the monitor's native color space. However, if the conversion was done in 8 bits, (255,0,0) would be translated to (246,0,0), and there would now only be 247 available levels for the red channel instead of 256, degrading the displayed image quality. My question is: how does this work on Ubuntu? Let's say that I use Firefox (which is color-aware and uses ICC color profiles). Would I get 10-bit processing, thus preserving all levels of an 8-bit picture? What is the situation like for other applications, especially photo applications like Shotwell, Rawtherapee, Darktable, RawStudio, Photivo etc? Does Ubuntu differ from other operating systems (Linux and others) on this point?

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  • Build a view frustum from angles

    - by MulletDevil
    I have 4 angles, left, right, top & bottom. These angles are in degrees. They define the angle between the forward vector and the corresponding side. I am trying to use these to calculate the required values for Perseective Off Centre function found here http://docs.unity3d.com/Documentation/ScriptReference/Camera-projectionMatrix.html I tried doing (near plane-far plane) * Tan(angle) But that didn't give the correct results.

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  • What if globals make sense?

    - by Greg
    I've got a value that many objects need. For example, a financial application with different investments as objects, and most of them need the current interest rate. I was hoping to encapsulate my "financial environment" as an object, with the interest rate as a property. But, sibling objects that need that value can't get to it. So how do I share values among many objects without over-coupling my design? Obviously I'm thinking about this wrong.

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  • Strategy to use two different measurement systems in software

    - by Dennis
    I have an application that needs to accept and output values in both US Custom Units and Metric system. Right now the conversion and input and output is a mess. You can only enter in US system, but you can choose the output to be US or Metric, and the code to do the conversions is everywhere. So I want to organize this and put together some simple rules. So I came up with this: Rules user can enter values in either US or Metric, and User Interface will take care of marking this properly All units internally will be stored as US, since the majority of the system already has most of the data stored like that and depends on this. It shouldn't matter I suppose as long as you don't mix unit. All output will be in US or Metric, depending on user selection/choice/preference. In theory this sounds great and seems like a solution. However, one little problem I came across is this: There is some data stored in code or in the database that already returns data like this: 4 x 13/16" screws, which means "four times screws". I need the to be in either US or Metric. Where exactly do I put the conversion code for doing the conversion for this unit? The above already mixing presentation and data, but the data for the field I need to populate is that whole string. I can certainly split it up into the number 4, the 13/16", and the " x " and the " screws", but the question remains... where do I put the conversion code? Different Locations for Conversion Routines 1) Right now the string is in a class where it's produced. I can put conversion code right into that class and it may be a good solution. Except then, I want to be consistent so I will be putting conversion procedures everywhere in the code at-data-source, or right after reading it from the database. The problem though is I think that my code will have to deal with two systems, all throughout the codebase after this, should I do this. 2) According to the rules, my idea was to put it in the view script, aka last change to modify it before it is shown to the user. And it may be the right thing to do, but then it strikes me it may not always be the best solution. (First, it complicates the view script a tad, second, I need to do more work on the data side to split things up more, or do extra parsing, such as in my case above). 3) Another solution is to do this somewhere in the data prep step before the view, aka somewhere in the middle, before the view, but after the data-source. This strikes me as messy and that could be the reason why my codebase is in such a mess right now. It seems that there is no best solution. What do I do?

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  • use of Enum with flags in practice?

    - by user576510
    I just have read some stuff on enum today. Use of flags with enum was something interesting and new for me. But often practice and theoretical uses are different. I go through many articles they examples they quoted were good to get the concept but am still wondering in what situations one can use Enums with flag to store multiple values? Will highly appreciate if you please can share your practical experience of using enum with flags.

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  • Look-up Tables in SQL

    Lookup tables can be a force for good in a relational database. Whereas the 'One True Lookup Table' remains a classic of bad database design, an auxiliary table that holds static data, and is used to lookup values, still has powerful magic. Joe Celko explains.... NEW! SQL Monitor 2.0Monitor SQL Server Central's servers withRed Gate's new SQL Monitor.No installation required. Find out more.

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  • All hail the Excel Queen

    - by Tim Dexter
    An excellent question this past week from dear ol Blighty; actually from Brian at Nextgen Clearing Ltd in the big smoke (London). Brian was developing an excel template and wanted to be able to reference the data fields multiple times inside the Excel template. Damn good question and I of course has some wacky solutions, from macros and cell referencing in Excel to pre-processing the data with an XSL stylesheet to copy the data multiple times so it could be referenced multiple times. All completely outlandish, enter our Queen of Excel, Shirley from the development team. Shirley is singlehandedly responsible for the Excel templates, I put her through six months of hell a few years back, with a host of Excel template requirements. She was more than up to the challenge and has developed some great features. One of those, is the ability to use the hidden XDO_METADATA sheet to map the data to custom named fields so they can be used multiple times in the template. So simple and very neat! Excel template and regular Excel users will know that you can only use the naming function once ie the names have to be unique across the workbook so you can not reuse a cell/group name. To get around this you can just come up with as many cell names as you want and map them in the XDO_METADATA sheet to the data columns/fields in your XML data set:. For example: XDO_?DEPTNO_SUMMARY?  <?DEPTNO?> XDO_?DNAME_SUMMARY?  <?DNAME?> XDO_GROUP_?G_D_DETAIL? <xsl:for-each-group select=".//G_D" group-by="./DEPTNO"> XDO_?DEPTNO_DETAIL? <?DEPTNO?> As you can see DEPTNO has been referenced twice and mapped to different named values in the left hand column. These values can then be used to name individual cells in the Excel template. You'll also notice a mix of Publisher <? ...?> and native XSL commands. So the world is your oyster on the mapping and the complexity you might need for calculations or string manipulation. Shirley has kindly built out a sample Excel template, data and result here so you can see how it all hangs together. the XDO_METADATA sheet is hidden, just right click on the sheet names and use the Unhide command to show it.

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  • Why do we need to put N before strings in Microsoft SQL Server?

    - by user61752
    I'm learning T-SQL. From the examples I've seen, to insert text in a varchar() cell, I can write just the string to insert, but for nvarchar() cells, every example prefix the strings with the letter N. I tried the following query on a table which has nvarchar() rows, and it works fine, so the prefix N is not required: insert into [TableName] values ('Hello', 'World') Why the strings are prefixed with N in every example I've seen? What are the pros or cons of using this prefix?

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  • Eliminating Magic Numbers: When is it time to say "No"?

    - by oosterwal
    We're all aware that magic numbers (hard-coded values) can wreak havoc in your program, especially when it's time to modify a section of code that has no comments, but where do you draw the line? For instance, if you have a function that calculates the number of seconds between two days, do you replace seconds = num_days * 24 * 60 * 60 with seconds = num_days * HOURS_PER_DAY * MINUTES_PER_HOUR * SECONDS_PER_MINUTE At what point do you decide that it is completely obvious what the hard-coded value means and leave it alone?

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  • Is return-type-(only)-polymorphism in Haskell a good thing?

    - by dainichi
    One thing that I've never quite come to terms with in Haskell is how you can have polymorphic constants and functions whose return type cannot be determined by their input type, like class Foo a where foo::Int -> a Some of the reasons that I do not like this: Referential transparency: "In Haskell, given the same input, a function will always return the same output", but is that really true? read "3" return 3 when used in an Int context, but throws an error when used in a, say, (Int,Int) context. Yes, you can argue that read is also taking a type parameter, but the implicitness of the type parameter makes it lose some of its beauty in my opinion. Monomorphism restriction: One of the most annoying things about Haskell. Correct me if I'm wrong, but the whole reason for the MR is that computation that looks shared might not be because the type parameter is implicit. Type defaulting: Again one of the most annoying things about Haskell. Happens e.g. if you pass the result of functions polymorphic in their output to functions polymorphic in their input. Again, correct me if I'm wrong, but this would not be necessary without functions whose return type cannot be determined by their input type (and polymorphic constants). So my question is (running the risk of being stamped as a "discussion quesion"): Would it be possible to create a Haskell-like language where the type checker disallows these kinds of definitions? If so, what would be the benefits/disadvantages of that restriction? I can see some immediate problems: If, say, 2 only had the type Integer, 2/3 wouldn't type check anymore with the current definition of /. But in this case, I think type classes with functional dependencies could come to the rescue (yes, I know that this is an extension). Furthermore, I think it is a lot more intuitive to have functions that can take different input types, than to have functions that are restricted in their input types, but we just pass polymorphic values to them. The typing of values like [] and Nothing seems to me like a tougher nut to crack. I haven't thought of a good way to handle them. I doubt I am the first person to have had thoughts like these. Does anybody have links to good discussions about this Haskell design decision and the pros/cons of it?

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  • Easy QueryBuilder - A User-Friendly Ad-Hoc Advanced Search Solution

    Constructing an easy and powerful QueryBuilder interface becomes more important for complex data grid filtering and accurate reporting services. In this article, I'll discuss how to build a query search engine using ASP.NET AJAX and dynamic SQL. The main goal is to provide an interactive interface to allow users select query attributes, operators, attribute values, and T-SQL operators so that the data context query list can be easily composed and a search engine is invoked.

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  • How can I ease the work of getting pixel coordinates from a spritesheet?

    - by ThePlan
    When it comes to spritesheets they're usually easier to use, and they're very efficient memory-wise, but the problem that I'm always having is getting the actual position of a sprite from a sheet. Usually, I have to throw in some aproximated values and modify them several times until I get it right. My question: is there a tool which can basically show you the coordinates of the mouse relative to the image you have opened? Or is there a simpler method of getting the exact rectangle that the sprite is contained in?

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  • RadioButtons and Lambda Expressions

    - by MightyZot
    Radio buttons operate in groups. They are used to present mutually exclusive lists of options. Since I started programming in Windows 20 years ago, I have always been frustrated about how they are implemented. To make them operate as a group, you put your radio buttons in a group box. Conversely, to group radio buttons in HTML, you simply give them all the same name. Radio buttons with the same name or ID in HTML operate as one mutually exclusive group of options. In C#, all your radio buttons must have unique names and you use group boxes to group them. I’m in the process of converting some old code to C# and I’m tasked with creating a user control with groups of radio buttons on it. I started out writing the traditional switch…case statements to check the appropriate radio button based upon value, loops to uncheck them all, etc. Then it occurred to me that I could stick the radio buttons in a Dictionary or List and use Lambda expressions to make my code a lot more maintainable. So, here is what I ended up with: Here is a dictionary that contains my list of radio buttons and their values. I used their values as the keys, so that I can select them by value. Now, instead of using loops and switch…case statements to control the radio buttons, I use the lambda syntax and extension methods. Selecting a Radio Button by Value This code is inside of a property accessor, so “value” represents the value passed into the property accessor. The “First” extension method uses the delegate represented by the lambda expression to select the radio button (actually KeyValuePair) that represents the passed in value. Finally, the resulting checkbox is checked. Since the radio buttons are in the same group, they function as a group, the appropriate radio button is selected while the others are unselected. Reading the Value This is the get accessor for the property that returns the value of the checked radio button. Now, if you’re using binding, this code is likely not necessary; however, I didn’t want to use binding in this case, so I think this is a good alternative to the traditional loops and switch…case statements.

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  • Do not expose enum in WCF response

    - by Michael Freidgeim
    We had a backward compatibility problem in WCF client, when in Service application a new value was added to one of enums. We discussed different ways to avoid this backward compatibility issues, and I found recommendation do not expose enum in wcf response in http://stackoverflow.com/a/788281/52277.It is still required to create new versions of our service interfaces to replace each enum fields with string field, that expects only documented values, and describe, what should be default behavior, if field has an unexpected value.

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  • How would one build a relational database on a key-value store, a-la Berkeley DB's SQL interface?

    - by coleifer
    I've been checking out Berkeley DB and was impressed to find that it supported a SQL interface that is "nearly identical" to SQLite. http://docs.oracle.com/cd/E17076_02/html/bdb-sql/dbsqlbasics.html#identicalusage I'm very curious, at a high-level, how this kind of interface might have been architected. For instance: since values are "transparent", how do you efficiently query and sort by value how are limits and offsets performed efficiently on large result sets how would the keys be structured and serialized for good average-case performance

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  • How much of a benefit does a changing landing page give in terms of SEO?

    - by Glycan
    I have a friend with a small business with a website. He asked me if he should make a put a section on his landing page under the fold that with his most recent review (or something along those lines). Specifically, he wants to know if that's the most efficient use of his time. Is there a list or such of things google values compared to each other, so that these kinds of answers could be easily answered?

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  • What common programming problems are best solved by using prototypes and closures?

    - by vemv
    As much as I understand both concepts, I can't see how can I take advantage of JavaScript's closures and prototypes aside from using them for creating instantiable and/or encapsulated class-like blocks (which seems more of a workaround than an asset to me) Other JS features such as functions-as-values or logical evaluation of non-booleans are much easier to fall in love with... What common programming problems are best solved by using propotypal inheritance and closures?

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  • How can I do fast Triangle/Square vs Triangle collision detection?

    - by Ólafur Waage
    I have a game world where the objects are in a grid based environment with the following restrictions. All of the triangles are 45-90-45 triangles that are unit length. They can only rotate 90°. The squares are of unit length and can not rotate (not that it matters) I have the Square vs Square detection down and it is very very solid and very fast (max vs min on x and y values) Wondering if there are any tricks I can employ since I have these restrictions on the triangles?

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  • Why do most programming languages only support returning a single value from a function?

    - by M4N
    Is there a reason or an explanation why functions in most(?) programming languages are designed to support any number of input parameters but only one return value? In most languages, it is possible to "work around" that limitation, e.g. by using out-parameters, returning pointers or by defining/returning structs/classes. But it seems strange, that programming languages were not designed to support multiple return values in a more "natural" way.

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  • Code testing practice

    - by Robin Castlin
    So now I have come to the conclusion like many others that having some way of constantly testing your code is good practice since it enables fewer people to be involved (colleges and customers alike) by simply knowing what's wrong before someone else finds out the hard way. I've heard and read some about Unit Testing and understand what it's supposed to do and all. The there are so many different types of bugs. It can be everything from web browser not being able not being able to send correct values, javascript failing, a global function messing up a piece of code somewhere to a change that looked good when testing it out but fails in some special case which was hard to anticipate. My simply finding these errors I learn to rarely repeat them again, but there seems to always be new bugs to be found and learnt from. I would guess maybe the best practice would be to run every page and it's functions a couple of times, witness the result and repeat this in Firefox, Chrome and Internet Explorer (and all smartphones apparently) to make sure it works as intended. However this would take quite some time to do consider I don't work with patches/versions and do little fixes here and there a couple of times per week. What I prefer would be some kind of page I can just load that tests as much things as possible to make sure the site works as intended. Basicly just run a lot of cURL's with POST-values and see if I get expected result. But how would I preferably not increase the IDs of every mysql rows if I delete these testing rows? It feels silly to be on ID 1000 with maybe 50 rows in total. If I could build a new project from scratch I would probably implement some kind of smooth way to return a "TRUE" on testing instead of the actual page. But this solution would for the moment being have to be passed on existing projects. My question What would you recommend to be the best way to test my site to make sure that existing functions does their job upon editing the code? Should I consider to implement a lot of edits first, then test manually the entire code to make sure it still works? Is there any nice way of testing codes without "hurting" the ID columns? Extra thoughs Would it be a good idea to associate all of my files to the different parts of my site which they affect? For instance if I edit home.php I will through documentation test if my homepage's start works as intended since it's the only part of my site it should affect.

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  • SQL Server 2012 Integration Services - Package and Project Configurations

    Marcin Policht examines SSIS 2012 package and project configurations, which offer different ways of modifying values of variables and parameters without having to directly edit content of the packages and projects of which they are a part. Get smart with SQL Backup ProGet faster, smaller backups with integrated verification.Quickly and easily DBCC CHECKDB your backups. Learn more.

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  • Reporting what's not there

    It's easy to write queries that will show data in the database that matches a criteria. However, if no data in the database matches the criteria, it becomes more difficult. This article examines two different scenarios where it's necessary to create data in order to be able to report zero values in queries.

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  • Working with SQL Agent Durations

    SQL Agent stores duration in HHMMSS format - not always useful. Discover how to use Powershell, some basic math, and T-SQL to tame these unruly values. Learn Agile Database Development Best PracticesAgile database development experts Sebastian Meine and Dennis Lloyd are running day-long classes designed to complement Red Gate’s SQL in the City US tour. Classes will be held in San Francisco, Chicago, Boston and Seattle. Register Now.

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