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  • Find the centroid of a polygon with weighted vertices

    - by Calle Kabo
    Hi, I know how to find the centroid (center of mass) of a regular polygon. This assumes that every part of the polygon weighs the same. But how do I calculate the centroid of a weightless polygon (made from aerogel perhaps :), where each vertex has a weight? Simplified illustration of what I mean using straight line: 5kg-----------------5kg ^center of gravity 10kg---------------5kg ^center of gravity offset du to weight of vertices Of course, I know how to calculate the center of gravity on a straight line with weighted vertices, but how do I do it on a polygon with weighted vertices? Thanks for your time!

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  • kmeans based on mapreduce by python

    - by user3616059
    I am going to write a mapper and reducer for the kmeans algorithm, I think the best course of action to do is putting the distance calculator in mapper and sending to reducer with the cluster id as key and coordinates of row as value. In reducer, updating the centroids would be performed. I am writing this by python. As you know, I have to use Hadoop streaming to transfer data between STDIN and STOUT. according to my knowledge, when we print (key + "\t"+value), it will be sent to reducer. Reducer will receive data and it calculates the new centroids but when we print new centroids, I think it does not send them to mapper to calculate new clusters and it just send it to STDOUT and as you know, kmeans is a iterative program. So, my questions is whether Hadoop streaming suffers of doing iterative programs and we should employ MRJOB for iterative programs?

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  • Can I tell if the iPhone has a passcode?

    - by tewha
    I'm developing an application that asks for a PIN when you start it. That's not great, but I can live with it. The problem is I'm being asked to ask for the PIN each time the phone wakes from sleep, too. Combined with the OS asking for its passcode, it's too much. Is there any legitimate way to detect if the phone has a passcode required for waking, so I can skip requiring a PIN in this case? I don't want to know the PIN and I don't actually care if it was locked (for instance, if the phone was asleep very briefly), I just want to know that the data is in some way "protected."

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  • Can you pass _POST variables from 1 server to another?

    - by Dr. DOT
    I have a web form on an IIS server (has no PHP). I have a PHP script on a LAMP server. My _POST var array is coming up empty on the LAMP server. My suspicion is I cannot pass POST vars from 1 server to another but I would like to have that confirmed. Does anyone know the answer to this? If that's the case then I know I need to with use _GET vars in the URL's Query String or set a cookie (which I can do because both servers are config'd with the domain name). Thanks for your help.

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  • Using Closure Properties to prove Regularity

    - by WATWF
    Here's a homework problem: Is L_4 Regular? Let L_4 = L*, where L={0^i1^i | i>=1}. I know L is non-regular and I know that Kleene Star is a closed operation, so my assumption is that L_4 is non-regular. However my professor provided an example of the above in which L = {0^p | p is prime}, which he said was regular by proving that L* was equal to L(000* + e) by saying each was a subset of one another (e in this case means the empty word). So his method involved forming a regex of 0^p, but how I can do that when I essentially have one already?

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  • mysql syntax how to add a third table to $query

    - by IberoMedia
    I have code: $query = "SELECT a.*, c.name as categoryname, c.id as categoryid". " FROM #__table_one as a". " LEFT JOIN #__table_two c ON c.id = a.catid"; $query .= " WHERE a.published = 1" ." AND a.access <= {$aid}" ." AND a.trash = 0" ." AND c.published = 1" ." AND c.access <= {$aid}" ." AND c.trash = 0" ; I would like to add a third table ('__some_table') for the parts of the query where a.publish, a.access and a.trash. In other words, I want these fields to be retrieved from another table, not "#__table_one", but I do not know how to incorporate the #__some_table into the current query I imagine the JOIN command can help me, but I do not know how to code mysql Thank you,

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  • Processing variable number of form fields

    - by a_m0d
    I am working on a form which displays information about orders. Each order has a unique id, but they are not necessarily sequential on the form. Also, the number of fields can vary (one field per row on the form). The input into the form will not be mapped straight into the database, but will be added to the current value in the database, and then saved. An example of the form is in the picture below - the callout on the right shows the id for each row. I know how to generate the form like this, but I can't work out how I can easily process each of these rows reliably. I also know how to give each of the fields a unique identifier, like name="row-23", but how can I translate that name so that I can update the related record in the database?

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  • MS Access 07 - Q re lookup column vs many-to-many; Q re checkboxes in many-to-many forms

    - by TBinLondon
    Hello, I'm creating a database with Access. This is just a test database, similar to my requirements, so I can get my skills up before creating one for work. I've created a database for a fictional school as this is a good playground and rich data (many students have many subjects have many teachers, etc). Question 1 What is the difference, if any, between using a Lookup column and a many-to-many associate table? Example: I have Tables 'Teacher' and 'Subject'. Many teachers have many subjects. I can, and have, created a table 'Teacher_Subject' and run queries with this. I have then created a lookup column in teachers table with data from subjects. The lookup column seems to take the place of the teacher_subject table. (though the data on relationships is obviously duplicated between lookup table and teacher_subject and may vary). Which one is the 'better' option? Is there a snag with using lookup tables? (I realize that this is a very 'general' question. Links to other resources and answers saying 'that depends...' are appreciated) Question 2 What attracts me to lookup tables is the following: When creating a form for entering subjects for teachers, with lookup I can simply create checkboxes and click a subject for a teacher 'on' or 'off'. Each click on/off creates/removes a record in the lookup column (which replaces teacher_subject). If I use a form from a query from teacher subject with teacher as main form and subject as subform I run into this problem: In the subform I can either select each subject that teacher has in a bombo box, i.e. click, scroll down, select, go to next row, click, scroll down, etc. (takes too long) OR I can create a list box listing all available subjects in each row but allowing me to select only one. (takes up too much space). Is it possible to have a click on/off list box for teacher_subject, creating/removing a record there with each click? Note - I know zero SQL or VB. If the correct answer is "you need to know SQL for this" then that's cool. I just need to know. Thanks!

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  • Will MySql caching cause performance problems?

    - by Camran
    I am about to upload my website onto a VPS. It is a classifieds website, where all data is stored in MySql and Solr. I wonder if when using MySql:s cache, the server will slow down? Ie, if somebody makes a search for the first time, and MySql is to cache the query, will the caching make the server slower than if it would not cache anything? After the caching is done I know things will improve in terms of performance... But I would like to know if I should even use the cache or not, what do you think? Thanks

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  • C++ Segementation fault in binary_function

    - by noryb009
    I'm using Visual Studio 2010 Beta 2 (also tried with NetBeans), and I'm having a segmentation fault in the following code: // One of the @link s20_3_3_comparisons comparison functors@endlink. template <class _Tp> struct less : public binary_function<_Tp, _Tp, bool> { bool operator()(const _Tp& __x, const _Tp& __y) const { return __x < __y; } //this is the problem line }; I don't know what in my program calls it, but I am trying to find out. (I think it's a map) Does anyone know what to do, or has encountered this before?

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  • Iphone SDK on Windows (alternative solutions)

    - by Cyclone
    I know there is no official SDK for windows, which is very annoying. Is there any way to develop applications on a windows computer, other than somehow running a mac os in vmware? I know you can do it with Xcode, but that is also only for macs. Google searches have revealed absolutely nothing...... If I cannot use the SDK or Xcode, any way I can just check syntax or something and just make my code in Notepad and save it with the proper extension? I have no idea whether or not I would be able to do that, probably because I have never even tried the SDK and probably never will without buying a mac.

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  • input in search box programmatically

    - by Sahil Manchanda
    I'm making a Java program where I programmatically insert data into search field of a website and make submit event programmatically . after submission a new website is opened.. i know i can read data using URLCONNECTION. Eg if website name is www.pqr.net/index.php after I make search submission I'm redirected to that page. eg. www.pqr.net/ind2.php how to get the url of page where I'm redirected because I want to read the contents of that page , unless I don't know the url of the page where I'm redirected , I can't read the contents

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  • Generic Abstract Singleton with Custom Constructor in C#

    - by Heka
    I want to write a generic singleton with an external constructor. In other words the constructor can be modified. I have 2 designs in my mind but I don't know whether they are practical or not. First one is to enforce derived class' constructor to be non-public but I do not know if there is a way of it? Second one is to use a delegate and call it inside the constructor? It isn't necessarily to be a constructor. The reason I chose custom constructor is doing some custom initializations. Any suggestions would be appreciated :)

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  • Should I dive into ASP.NET MVC or start with ASP.NET Webforms?

    - by Sahat
    I plan to pick up Silverlight in the future. Possibility of going into Microsoft WPF. Currently learning Objective-C 2.0 w/ Cocoa. I already know Pros and Cons of ASP.NET MVC vs ASP.NET Webforms. What I want to know is what would be more "efficient" for me to learn given the circumstances above? By efficient I mean learning one design pattern once and then re-using it. Objective-C I believe uses MVC approach? What about Silverlight? WPF? So what do you think? Also as a side question is it true that ASP.NET Webforms is often used by freelancers/small companies and ASP.NET MVC in large enterprises?

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  • How to grab all cookies in Flash

    - by Leticia Meyer
    For a site I'm developing with a user login that uses cookies to store the session ID, a separate section of it uses Flash to provide content and such. Is there some way it can access the cookies that were set the by login? The name of the cookie will not the be same every time, as it is randomly generated, as well as its value. I then need to send the name and value of the cookie back to a page on the server to do additional stuff. Anyone know how to do this? Note that I didn't write the Flash interface, an the person who did doesn't know how to do this. Please help me, and thanks in advance!

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  • What's the difference between /123 and /?123?

    - by BoltClock
    I've noticed that some sites (including http://jobs.stackoverflow.com) have query strings that look like this: http://somewebapp.example/?123 as compared to: http://somewebapp.example/123 or http://somewebapp.example/id/123 What are the reasons that developers choose to implement their web apps' URLs using the first example instead of the second and third examples? And as a bonus, how would one implement the first example in PHP, given that 123 is the primary key of some row in a database table? (I just need to know how to retrieve 123 from the URL; I already know how to query the database for a primary key of 123.)

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  • android exit application completely and go to main applications screen

    - by Totti
    i know that this question is asked many times, but really i can't understand the answer, i want to set button, when user click it i want to exit the application (also the carbage collector should remove the objects), and after exiting i want to go to the screen where the user found the application icon on mobile. for exit i don't know what to do for going to the screen where to find the application icon i tried like this Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(intent); but doesn't work

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  • Movable Type: Specify one category to display in entry

    - by kohei
    Hi I want to specify one <CategoryLabel> in <MTEntryCategories> in archive template. For example my categories are like this (x is selected category in entry): Fruit --Apple --Grape Drinks --Coffee -x-Beer --Juice Vacation --France -x-UK In this case I want to display the label under "Drinks" in a entry (sample code) <MTSubCategories category="Drinks"> <MTEntryCategories> <h1><$MTcategory_label$><h1> </MTEntryCategories> </MTSubCategories> I know there are various plugin that do this but I couldn't find one that supports MT5. If anyone know if there is a way to do this without the plugins, greatly appreciated!

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  • Send xml from ActionScript to PHP

    - by Vish
    Hi, I have values inside an XMLList in Actionscript. Need to send these values to the DB and update it. My actionscript code is as follows: http://www.freeimagehosting.net/uploads/dbbc612193.gif How can I send the XMLList data to PHP? Should I add a toString() to it? Also what should be the contentType in Flex. How can I catch this inside PHP, pl let me know, trying to use, this way, if($user - isAllowedAccess()) { header("Content-type:text/xml"); $postedData = $_POST["pdata"]; // $xmldoc = simplexml_load_string($POST['pdata']); // echo($xmldoc); } No luck. Pl let me know.

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  • In SQL Server, can multiple inserts be replaced with a single insert that takes an XML parameter?

    - by Mayo
    So I have an existing ASP.NET solution that uses LINQ-to-SQL to insert data into SQL Server (5 tables, 110k records total). I had read in the past that XML could be passed as a parameter to SQL Server but my google searches turn up results that store the XML directly into a table. I would rather take that XML parameter and insert the nodes as records. Is this possible? How is it done (i.e. how is the XML parameter used to insert records in T-SQL, how should the XML be formatted)? Note: I'm researching other options like SQL bulk copy and I know that SSIS would be a good alternative. I want to know if this XML approach is feasible.

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