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  • Information Gain and Entropy

    - by dhorn
    I recently read this question regarding information gain and entropy. I think I have a semi-decent grasp on the main idea, but I'm curious as what to do with situations such as follows: If we have a bag of 7 coins, 1 of which is heavier than the others, and 1 of which is lighter than the others, and we know the heavier coin + the lighter coin is the same as 2 normal coins, what is the information gain associated with picking two random coins and weighing them against each other? Our goal here is to identify the two odd coins. I've been thinking this problem over for a while, and can't frame it correctly in a decision tree, or any other way for that matter. Any help? EDIT: I understand the formula for entropy and the formula for information gain. What I don't understand is how to frame this problem in a decision tree format. EDIT 2: Here is where I'm at so far: Assuming we pick two coins and they both end up weighing the same, we can assume our new chances of picking H+L come out to 1/5 * 1/4 = 1/20 , easy enough. Assuming we pick two coins and the left side is heavier. There are three different cases where this can occur: HM: Which gives us 1/2 chance of picking H and a 1/4 chance of picking L: 1/8 HL: 1/2 chance of picking high, 1/1 chance of picking low: 1/1 ML: 1/2 chance of picking low, 1/4 chance of picking high: 1/8 However, the odds of us picking HM are 1/7 * 5/6 which is 5/42 The odds of us picking HL are 1/7 * 1/6 which is 1/42 And the odds of us picking ML are 1/7 * 5/6 which is 5/42 If we weight the overall probabilities with these odds, we are given: (1/8) * (5/42) + (1/1) * (1/42) + (1/8) * (5/42) = 3/56. The same holds true for option B. option A = 3/56 option B = 3/56 option C = 1/20 However, option C should be weighted heavier because there is a 5/7 * 4/6 chance to pick two mediums. So I'm assuming from here I weight THOSE odds. I am pretty sure I've messed up somewhere along the way, but I think I'm on the right path! EDIT 3: More stuff. Assuming the scale is unbalanced, the odds are (10/11) that only one of the coins is the H or L coin, and (1/11) that both coins are H/L Therefore we can conclude: (10 / 11) * (1/2 * 1/5) and (1 / 11) * (1/2) EDIT 4: Going to go ahead and say that it is a total 4/42 increase.

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  • Does the order of columns matter in a group by clause?

    - by Jeff Meatball Yang
    If I have two columns, one with very high cardinality and one with very low cardinality (unique # of values), does it matter in which order I group by? Here's an example: select dimensionName, dimensionCategory, sum(someFact) from SomeFact f join SomeDim d on f.dimensionKey = d.dimensionKey group by d.dimensionName, -- large number of unique values d.dimensionCategory -- small number of unique values Are there situations where it matters?

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  • Sorting a list of colors in one dimension?

    - by Ptah- Opener of the Mouth
    I would like to sort a one-dimensional list of colors so that colors that a typical human would perceive as "like" each other are near each other. Obviously this is a difficult or perhaps impossible problem to get "perfectly", since colors are typically described with three dimensions, but that doesn't mean that there aren't some sorting methods that look obviously more natural than others. For example, sorting by RGB doesn't work very well, as it will sort in the following order, for example: (1) R=254 G=0 B=0 (2) R=254 G=255 B=0 (3) R=255 G=0 B=0 (4) R=255 G=255 B=0 That is, it will alternate those colors red, yellow, red, yellow, with the two "reds" being essentially imperceivably different than each other, and the two yellows also being imperceivably different from each other. But sorting by HLS works much better, generally speaking, and I think HSL even better than that; with either, the reds will be next to each other, and the yellows will be next to each other. But HLS/HSL has some problems, too; things that people would perceive as "black" could be split far apart from each other, as could things that people would perceive as "white". Again, I understand that I pretty much have to accept that there will be some splits like this; I'm just wondering if anyone has found a better way than HLS/HSL. And I'm aware that "better" is somewhat arbitrary; I mean "more natural to a typical human". For example, a vague thought I've had, but have not yet tried, is perhaps "L is the most important thing if it is very high or very low", but otherwise it is the least important. Has anyone tried this? Has it worked well? What specifically did you decide "very low" and "very high" meant? And so on. Or has anyone found anything else that would improve upon HSL? I should also note that I am aware that I can define a space-filling curve through the cube of colors, and order them one-dimensionally as they would be encountered while travelling along that curve. That would eliminate perceived discontinuities. However, it's not really what I want; I want decent overall large-scale groupings more than I want perfect small-scale groupings. Thanks in advance for any help.

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  • IE Automation - How to Trap 'NewProcess' event

    - by dpb
    In Environment - Standard User, Win7x64, IE8 on opening Unprotected URL, IE 8 will first start a tab with low integrity and the swap out this tab with another tab of medium integrity. This is done behind the scene and the original IWebBrowser2 pointer is lost. I want to catch the 'NewProcess' Event which will get generated during this swap out, please help me how to go about this. Sample code can help me, me using C++ Ref - http://blogs.msdn.com/b/ieinternals/archive/2011/08/03/internet-explorer-automation-protected-mode-lcie-default-integrity-level-medium.aspx Thank You

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  • Is it possible to implement Separated Interface in PHP?

    - by sunwukung
    I recently asked a question regarding the resolution of dependencies between Unit of Work and Data Mapper classes: http://stackoverflow.com/questions/3012657/dependency-injection-and-unit-of-work-pattern - (which was answered by Gabor de Mooij - thx) In PoEAA, Martin Fowler suggests using Separated Interface to manage these dependencies. My question is simple - is it actually possible to implement this pattern in PHP, or is it specific to Java interfaces? I've searched high and low and it's hard to find references to this pattern anywhere outside of PoEAA.

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  • WinForms notifyicon high dpi

    - by Dubila
    in my c# application (2.0 framework) I'm using notifyicon. I set the icon to an ico file that contains 16X16 and 32X32 icons. when I change the DPI to 150% in win7 the icon looks the 16X16 icon. it looks with very low resolution.

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  • High-level languages for out-of-the-box GUI desktop application programming

    - by Omeoe
    After I discontinued programming in C++ while entering into web authoring I was spoilt by PHP's high level constructs like hash tables or its dynamic, weak typing. I remembered the angst of C/C++ pointers and the maze of low-level Win32 API handles and message loops and that prevented me from utilizing environments like Code::Blocks for desktop applications. I am also not very fond of bulky, statically-typed C#/.NET environment. Any other ideas?

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  • ADO.NET Data Services for MySQL

    - by Shalan
    Hey! I've searched high and low for this, and no luck. Is there a way that CRUD methods for a MySQL install (Linux box) be exposed via ADO.NET WCF Data Services? I would really love to leverage this in my WPF app :) Thank u!

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  • WinForms: How to prevent textbox from opening alt menu?

    - by Digiku
    I have this textbox I use to capture keyboard shortcuts for a preferences config. I use a low-level keyboard hook to capture keys and also prevent them from taking action, e.g. the Windows key, but the Alt key still comes through and makes my textbox lose focus. How can I block the Alt key, so the focus is kept unaltered at my textbox?

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  • is there anyway to know if your supposedly fully dedicated server is really a virtually resource-sha

    - by siran
    Hi, sometimes I feel my server not responding as smoothly as I would expect (i have a Intel(R) Xeon(TM) CPU 2.80GHz Quad Core), given that for example, the 'top' commands reports a low load < 0.5, CPU are almost completely idle ... I maybe have internet connectivity issues, so I don't really know if it's me or if it's the server itself. Is there anykind of benchmarking script (or something analogous) I could run and see the actual performance of the server ?

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  • CDN with South America peering points / edge nodes

    - by Bill
    Hello, Does anyone one know of a CDN (Content Delivery Network) with true South American peering points or edge nodes? This seems to be quite rare. It seems that most CDNs serve Central and South America from Texas. However, our application requires low latency in Brazil, so this is not a good solution for us. We would like to avoid having to set up servers in South America just for this piece of the application, but may end up doing that. Thanks, Bill

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  • UML diagram for application architecture?

    - by fayer
    i'm trying to map my whole application in a UML diagram and i wonder what diagram type i should use. im not doing this in class level, rather from a bird eye's perspective. single application object (patterns: singleton)(examples: CodeIgniter application) that composes multiple module objects (patterns: singleton, facades)(examples: guestbook, addressbook) that compose multiple low level stand alone objects (examples: mysql mapper, doctrine mapper) that compose various 3rd and in-house libraries (examples: doctrine, solr, xml-parser) what UML diagram is suited for this kind of overview presentation? thanks

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  • Implementing a logging library in .NET with a database as the storage medium

    - by Dave
    I'm just starting to work on a logging library that everyone can use to keep track of any sort of system information while the user is running our application. The simplest example so far is to track Info, Warnings, and Errors. I want all plugins to be able to use this feature, but since each developer might have a different idea of what's important to report, I want to keep this as generic as possible. In the C++ world, I would normally use something like a stl::pair<string,string> to act as a key value pair structure, and have a stl::list of these to act as a "row" in the log. The log cache would then be a list<list<pair<string,string>>> (ugh!). This way, the developers can use a const string key like INFO, WARNING, ERROR to have a consistent naming for a column in the database (for SELECTing specific types of information). I'd like the database to be able to deal with any number of distinct column names. For example, John might have an INFO row with a column called USER, and Bill might have an INFO row with a column called FILENAME. I want the log viewer to be able to display all information, and if one report doesn't have a value for INFO / FILENAME, those fields should just appear blank. So one option is to use List<List<KeyValuePair<String,String>>, and the another is to have the log library consumer somehow "register" its schema, and then have the database do an ALTER TABLE to handle this situation. Yet another idea is to have a table that's just for key value pairs, with a foreign key that maps the key value pairs back to the original log entry. I obviously don't want logging to bog down the system, so I only lock the log cache to make a copy of the data (and remove the already-copied data), then a background thread will dump the information to the database. My specific questions regarding this are: Do you see any performance issues? In other words, have you ever tried something like this and found that certain things just don't work well in practice? Is there a more .NETish way to implement the key value pairs, other than List<List<KeyValuePair<String,String>>>? Even if there is a way to do #2 better, is the ALTER TABLE idea I proposed above a Bad Thing? Would you recommend multiple databases over a single one? I don't yet have an idea of how frequently the log would get written to, but we ideally would like to have lots of low level information. Perhaps there should be a DB with a fixed schema only for the low level stuff, and then another DB that's more flexible for reporting information back to users.

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  • Scalability of Ruby on Rails versus PHP

    - by Daniel
    Can anyone comment on which is more scalable between RoR and PHP? I have heard that RoR is less scalable than PHP since RoR has a little more overhead with its MVC framework while PHP is more low level and lighter. This is a bit vague - can anyone explain better?

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  • real time scenario between interface/abstract class ?

    - by JavaUser
    Hi , Please give me a real time simple example for the below questions : Where to use interface rather abstract class Where to use abstract class rather interface I need code snippet for both . Which takes low memory and which performs well . Do I need to consider the design aspect also? What is the conceptual difference not the syntactical difference .

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  • What is a good PDF report generator tool for python?

    - by jlouis
    What is a good tool for PDF report generation in Python? I've checked out ReportLab, but it seems to be awfully low-level for what I want to do. My current hunch is to call TeX on the command-line and let it produce the PDF, but if there is something that is easier to work with (and looks professional - We'll send this to customers) I'd very much like a prod in the right direction.

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  • A lightweight application framework for PHP?

    - by millenomi
    I have long been a fan of _why's Camping microframework -- lightweight, great for microscopic applications (low concurrency, easy to use and edit and maintain), which is what I do. I'd love to know if there's something similar for PHP; full-blown app frameworks like CakePHP or Symphony are very large for what I do, but I can't seem to find nothing "less". What PHP framework would you prefer, in this situation?

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  • When to call glEnable(GL_FRAMEBUFFER_SRGB)?

    - by Steven Lu
    I have a rendering system where I draw to an FBO with a multisampled renderbuffer, then blit it to another FBO with a texture in order to resolve the samples in order to read off the texture to perform post-processing shading while drawing to the backbuffer (FBO index 0). Now I'd like to get some correct sRGB output... The problem is the behavior of the program is rather inconsistent between when I run it on OS X and Windows and this also changes depending on the machine: On Windows with the Intel HD 3000 it will not apply the sRGB nonlinearity but on my other machine with a Nvidia GTX 670 it does. On the Intel HD 3000 in OS X it will also apply it. So this probably means that I'm not setting my GL_FRAMEBUFFER_SRGB enable state at the right points in the program. However I can't seem to find any tutorials that actually tell me when I ought to enable it, they only ever mention that it's dead easy and comes at no performance cost. I am currently not loading in any textures so I haven't had a need to deal with linearizing their colors yet. To force the program to not simply spit back out the linear color values, what I have tried is simply comment out my glDisable(GL_FRAMEBUFFER_SRGB) line, which effectively means this setting is enabled for the entire pipeline, and I actually redundantly force it back on every frame. I don't know if this is correct or not. It certainly does apply a nonlinearization to the colors but I can't tell if this is getting applied twice (which would be bad). It could apply the gamma as I render to my first FBO. It could do it when I blit the first FBO to the second FBO. Why not? I've gone so far as to take screen shots of my final frame and compare raw pixel color values to the colors I set them to in the program: I set the input color to RGB(1,2,3) and the output is RGB(13,22,28). That seems like quite a lot of color compression at the low end and leads me to question if the gamma is getting applied multiple times. I have just now gone through the sRGB equation and I can verify that the conversion seems to be only applied once as linear 1/255, 2/255, and 3/255 do indeed map to sRGB 13/255, 22/255, and 28/255 using the equation 1.055*C^(1/2.4)+0.055. Given that the expansion is so large for these low color values it really should be obvious if the sRGB color transform is getting applied more than once. So, I still haven't determined what the right thing to do is. does glEnable(GL_FRAMEBUFFER_SRGB) only apply to the final framebuffer values, in which case I can just set this during my GL init routine and forget about it hereafter?

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  • Segment a CGImage

    - by mag725
    Hi, In iOS 4.0 and later is there a way to segment a CGImage without loading the entire image into memory? What I am attempting to do is * programmatically* segment an image for use in a CATiledLayer application using large images, but I don't want to take up the memory involved in loading the full image. Also, is there a way to load that (or any) segment at a particular resolution, so if we are zoomed out from the image we can load that tile at a low level of detail, thus saving memory. Thanks! -Matt

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  • I have problem loading all items from XML with for each

    - by vaha
    Hi all, I'm low level as3 programmer and I need help whit this code: I have gallery XML file: 1 0 Lokacije 1 1.jpg 2 2 Coaching 1 2.jpg 3 0 0 3.jpg And: var loader: URLLoader = new URLLoader(); loader.load(new URLRequest("gallery.xml"); var xml = new XML(evt.target.data); for each(var item in xml..item) { centralniText.htmlText = item.slika; } only shows last item from XML file: 3.jpg I want all. Please help.

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