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• Using ARIMA to model and forecast stock prices using user-friendly stats program

  - by Brian

  Hi people, Can anyone please offer some insight into this for me? I'm coming from a functional magnetic resonance imaging research background where I analyzed a lot of time series data, and I'd like to analyze the time series of stock prices (or returns) by: 1) modeling a successful stock in a particular market sector and then cross-correlating the time series of this historically successful stock with that of other newer stocks to look for significant relationships; 2) model a stock's price time series and use forecasting (e.g., exponential smoothing) to predict future values of it. I'd like to use non-linear modeling methods (ARIMA and ARCH) to do this. Several questions: How often do ARIMA and ARCH modeling methods (given that the individual who implements them does so accurately) actually fit the stock time series data they target, and what is the optimal fit I can expect? Is the extent to which this model fits the data commensurate with the extent to which it predicts this stock time series' future values? Rather than randomly selecting stocks to compare or model, if profit is my goal, what is an efficient approach, if any, to selecting the stocks I'm going to analyze? Which stats program is the most user-friendly for this? Any thoughts on this would be great and would go a long way for me. Thanks, Brian

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• Final classes in Python 3.x- something Guido isn't telling me?

  - by GlenCrawford

  This question is built on top of many assumptions. If one assumption is wrong, then the whole thing falls over. I'm still relatively new to Python and have just entered the curious/exploratory phase. It is my understanding that Python does not support the creating of classes that cannot be subclassed (final classes). However, it seems to me that the bool class in Python cannot be subclassed. This makes sense when the intent of the bool class is considered (because bool is only supposed to have two values: true and false), and I'm happy with that. What I want to know is how this class was marked as final. So my question is: how exactly did Guido manage to prevent subclassing of bool? >>> class TestClass(bool): pass Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> class TestClass(bool): TypeError: type 'bool' is not an acceptable base type Related question: http://stackoverflow.com/questions/2172189/why-i-cant-extend-bool-in-python

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• Mysql Server Optimization

  - by Ish Kumar

  Hi Geeks, We are having serious MySQL(InnoDB) performance issues at a moment when we do: (10-20) insertions on TABLE1 (10-20) updates on TABLE2 Note: Both above operations happens within fraction of a second. And this occurs every few (10-15) minutes. And all online users (approx 400-600) doing read operation on join of TABLE1 & TABLE2 every 1 second. Here is our mysql configuration info: http://docs.google.com/View?id=dfrswh7c_117fmgcmb44 Issues: Lot queries wait and expire later (saw it from phpmyadmin / processes). My poor MySQL server crashes sometimes Questions Q1: Any suggestions to optimize at MySQL level? Q2: I thinking to use persistent connections at application level, is it right? Info Added Later: Database Engine: InnoDB TABLE1 : 400,000 rows (inserting 8,000 daily) & TABLE2: 8,000 rows 1 second query: SELECT b.id, b.user_id, b.description, b.debit, b.created, b.price, u.username, u.email, u.mobile FROM TABLE1 b, TABLE2 u WHERE b.credit = 0 AND b.user_id = u.id AND b.auction_id = "12345" ORDER BY b.id DESC LIMIT 10; // there are few more but they are not so critical. Indexing is good, we are using them wisely. In above query all id's are indexed And TABLE1 has frequent insertions and TABLE2 has frequent updates.

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• Need variable width negative lookbehind replacement

  - by Technoh

  I have looked at many questions here (and many more websites) and some provided hints but none gave me a definitive answer. I know regular expressions but I am far from being a guru. This particular question deals with regex in PHP. I need to locate words in a text that are not surrounded by a hyperlink of a given class. For example, I might have This <a href="blabblah" class="no_check">elephant</a> is green and this elephant is blue while this <a href="blahblah">elephant</a> is red. I would need to match against the second and third elephants but not the first (identified by test class "no_check"). Note that there could more attributes than just href and class within hyperlinks. I came up with ((?<!<a .*class="no_check".*>)\belephant\b) which works beautifully in regex test software but not in PHP. Any help is greatly appreciated. If you cannot provide a regular expression but can find some sort of PHP code logic that would circumvent the need for it, I would be equally grateful.

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• Storing an object to use in multiple classes

  - by Aaron Sanders

  I am wondering the best way to store an object in memory that is used in a lot of classes throughout an application. Let me set up my problem for you: We have multiple databases, 1 per customer. We also have a master table and each row is detailed information about the databases such as database name, server IP it's located and a few config settings. I have an application that loops through those multiple databases and runs some updates on them. The settings I mentioned above are updated each loop iteration into memory. The application then runs through series of processes that include multiple classes using this data. The data never changes during the processes, only during the loop iteration. The variables are related to a customer, so I have them stored in a customer class. I suppose I could make all of the members shared or should I use a singleton for the customer class? I've never actually used a singleton, only read they are good in this type of situation. Are there better solutions to this type of scenario? Also, I could have plans for this application to be multithreaded later. Sorry if this is confusing. If you have questions, let me know and I will answer them. Thanks for your help.

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• return an ArrayList method

  - by Bopeng Liu

  This is a drive method for two other classes. which i posted here http://codereview.stackexchange.com/questions/33148/book-program-with-arraylist I need some help for the private static ArrayList getAuthors(String authors) method. I am kind a beginner. so please help me finish this drive method. or give me some directions. Instruction some of the elements of the allAuthors array contain asterisks “*” between two authors names. The getAuthors method uses this asterisk as a delimiter between names to store them separately in the returned ArrayList of Strings. import java.util.ArrayList; public class LibraryDrive { public static void main(String[] args) { String[] titles = { "The Hobbit", "Acer Dumpling", "A Christmas Carol", "Marley and Me", "Building Java Programs", "Java, How to Program" }; String[] allAuthors = { "Tolkien, J.R.", "Doofus, Robert", "Dickens, Charles", "Remember, SomeoneIdont", "Reges, Stuart*Stepp, Marty", "Deitel, Paul*Deitel, Harvery" }; ArrayList<String> authors = new ArrayList<String>(); ArrayList<Book> books = new ArrayList<Book>(); for (int i = 0; i < titles.length; i++) { authors = getAuthors(allAuthors[i]); Book b = new Book(titles[i], authors); books.add(b); authors.remove(0); } Library lib = new Library(books); System.out.println(lib); lib.sort(); System.out.println(lib); } private static ArrayList<String> getAuthors(String authors) { ArrayList books = new ArrayList<String>(); // need help here. return books; } }

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• WPF DataBinding to standard CLR properties in code-behind

  - by nukefusion

  Hi everyone, Just learning WPF databinding and have a gap in my understanding. I've seen a few similar questions on StackOverflow, but I'm still struggling in determining what I have done wrong. I have a simple Person class with a Firstname and Surname property (standard CLR properties). I also have a standard CLR property on my Window class that exposes an instance of Person. I've then got some XAML, with two methods of binding. The first works, the second doesn't. Can anybody help me to understand why the second method fails? There's no binding error message in the Output log. <Window x:Class="WpfApplication1.Window1" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" xmlns:local="clr-namespace:WpfApplication1" Title="Window1" Height="300" Width="300" DataContext="{Binding RelativeSource={RelativeSource Self}, Path=MyPerson}"> <StackPanel> <Label>My Person</Label> <WrapPanel> <Label>First Name:</Label> <Label Content="{Binding RelativeSource={RelativeSource AncestorType=Window, Mode=FindAncestor}, Path=MyPerson.FirstName}"></Label> </WrapPanel> <WrapPanel> <Label>Last Name:</Label> <Label Content="{Binding MyPerson.Surname}"></Label> </WrapPanel> </StackPanel> Edit: Ok, thanks so far. I've changed the second expression to: <Label Content="{Binding Surname}"></Label> I still can't get it to work though!

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• Building/Testing a Universal iPhone/iPad application

  - by psychotik

  I have a project configured (I think) to produce Universal binaries. The base SDK is set to 3.2 and the Deployment Target is set to 3.1. Target Device Family is iPhone/iPad and the architecture is armv6 armv7. I had a few questions about how this Universal binary thing really works: 1) When I want to submit an app binary for review, what configuration should I set as the build target? If I set it as "Device - 3.1" I get a warning which says "warning: building with Targeted Device Family" that includes iPad('1,2') requires building with the 3.2 or later SDK". However, if I build with SDK 3.2, will it still run on iPhones with OS 3.1? What's the right configuration for device and architecture (arm6/arm7)? 2) How do I test the scenario above (built with SDK 3.2, but installed on a device running OS 3.1)? If I build with SDK 3.2, when I try to install it on a phone with OS 3.1, I get an error saying that the phone's OS isn't updated. Thanks!

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• Really simple JSON serialization in .NET

  - by Evgeny

  I have some simple .NET objects I'd like to serialize to JSON and back again. The set of objects to be serialized is quite small and I control the implementation, so I don't need a generic solution that will work for everything. Since my assembly will be distributed as a library I'd really like to avoid a dependency on some third-party DLL: I just want to give users one assembly that they can reference. I've read the other questions I could find on converting to and from JSON in .NET. The recommended solution of JSON.NET does work, of course, but it requires distributing an extra DLL. I don't need any of the fancy features of JSON.NET. I just need to handle a simple object (or even dictionary) that contains strings, integers, DateTimes and arrays of strings and bytes. On deserializing I'm happy to get back a dictionary - it doesn't need to create the object again. Is there some really simple code out there that I could compile into my assembly to do this simple job? I've also tried System.Web.Script.Serialization.JavaScriptSerializer, but where it falls down is the byte array: I want to base64-encode it and even registering a converter doesn't let me easily accomplish that due to the way that API works (it doesn't pass in the name of the field).

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• find and replace values in a flat-file using PHP

  - by peirix

  I'd think there was a question on this already, but I can't find one. Maybe the solution is too easy... Anyway, I have a flat-file and want to let the user change the values based on a name. I've already sorted out creating new name+value-pairs using the fopen('a') mode, using jQuery to send the AJAX call with newValue and newName. But say the content looks like this: host|http:www.stackoverflow.com folder|/questions/ folder2|/users/ And now I want to change the folder value. So I'll send in folder as oldName and /tags/ as newValue. What's the best way to overwrite the value? The order in the list doesn't matter, and the name will always be on the left, followed by a |(pipe), the value and then a new-line. My first thought was to read the list, store it in an array, search all the [0]'s for oldName, then change the [1] that belongs to it, and then write it back to a file. But I feel there is a better way around this? Any ideas? Maybe regex?

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• Lift XML Parsing Error

  - by bstevens90

  I know there are other questions on this and I have read through almost all of them and none of them solved my problem. I have inside a home directory: def search(in: NodeSeq) : NodeSeq = { bind("work", in, "docId" -> text("", did = _), "visitId" -> text("", vid = _), "provider" -> text("", prov = _), "emCode" -> text(ecode, ecode = _)) } along with: <lift:home.searchForm form="POST" multipart="true" > <table> <tr> <td>DocId</td> <td>VisitId</td> <td>Provider</td> <td>EanMCode</td> </tr> <tr> <td><work:docId /></td> <td><work:visitId /></td> <td><work:provider /></td> <td><work:emCode /></td> <td><button>Click Me!</button></td> </tr> </table> </lift:home.searchForm> Inside an html page. I have included xmlns:lift="http://liftweb.net/" in default.... I can't find anyway to fix this... I am getting XML Parsing Error: prefix not bound to a namespace Location: http://localhost:8080/ Line Number 29, Column 10: <td><work:docId></work:docId></td> in firefox. I have written similar code and had it working in another app and just cant even find anything im doing different thats not trivial naming... Thanks in advance!

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• Creating circular generic references

  - by M. Jessup

  I am writing an application to do some distributed calculations in a peer to peer network. In defining the network I have two class the P2PNetwork and P2PClient. I want these to be generic and so have the definitions of: P2PNetwork<T extends P2PClient<? extends P2PNetwork<T>>> P2PClient<T extends P2PNetwork<? extends T>> with P2PClient defining a method of setNetwork(T network). What I am hoping to describe with this code is: A P2PNetwork is constituted of clients of a certain type A P2PClient may only belong to a network whose clients consist of the same type as this client (the circular-reference) This seems correct to me but if I try to create a non-generic version such as MyP2PClient<MyP2PNetwork<? extends MyP2PClient>> myClient; and other variants I receive numerous errors from the compiler. So my questions are as follows: Is a generic circular reference even possible (I have never seen anything explicitly forbidding it)? Is the above generic definition a correct definition of such a circular relationship? If it is valid, is it the "correct" way to describe such a relationship (i.e. is there another valid definition, which is stylistically preferred)? How would I properly define a non-generic instance of a Client and Server given the proper generic definition?

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• How to generate an ear file from a maven-archetype-webapp artifact?

  - by Mike

  I currently have a project built with maven-archetype-webapp artifact. The default packaging for this project is war. Is it possible for me to insert the maven-ear-plugin in this webapp pom.xml generate an ear file that contains this project war? I tried that, but the war file doesn't get embedded in the generated ear file. It has everything except the war file. I read many Maven related articles, and perhaps I could use maven-archetype-j2ee-simple artifact. However, I'm reluctant to this use for 2 reasons:- This artifact handles ejbs and all the extra features that I don't use. It makes my project looks bloated. Second, it seems like it requires me to install the web module into the repository first before I can create the ear file. Is this the preferred way to create an ear file? How do I create an ear file that contains the war file using maven-ear-plugin from my webapp's pom.xml? If this way is not possible, what's the preferred way? I'm sorry if my questions sound a little novice, I realized I have whole lot more to learn about Maven. Thanks much.

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• I Need a Human Readable, Yet Parse-able Document Format

  - by macinjosh

  I'm working on one of those projects where there are a million better ways to accomplish what I need but I have no choice and I have to do it this way. Here it is: There is a web form, when the user fills it out and hits a submit a human readable text file is created using the form data. It looks like this: field_1: value for field one field_2: value for field two more data for field two (field two has a newline in it!) field3: some more data My problem is this: I need to parse this text file back into the web form so that the user can edit it. How could I, in a foolproof way, accomplish this? A database is not an option, I have to use these text files. My Questions: Is there a foolproof way to do this using the format in the example above? What human readable format would work better (in other words I can change the format) Human readable means that a non programmer could read it and know what is what. This project uses PHP.

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• What is the basic pattern for using (N)Hibernate?

  - by Vilx-

  I'm creating a simple Windows Forms application with NHibernate and I'm a bit confused about how I'm supposed to use it. To quote the manual: ISession (NHibernate.ISession) A single-threaded, short-lived object representing a conversation between the application and the persistent store. Wraps an ADO.NET connection. Factory for ITransaction. Holds a mandatory (first-level) cache of persistent objects, used when navigating the object graph or looking up objects by identifier. Now, suppose I have the following scenario: I have a simple classifier which is a MSSQL table with two columns - ID (auto_increment) and Name (nvarchar). To edit this classifier I create a form which contains a single gridview and two buttons - OK and Cancel. The user can nearly directly edit the table in the gridview, and when he hits OK the changes he made are persisted to the DB (or if he hits cancel, nothing happens). Now, I have several questions about how to organize this: What should the lifetime of my ISession be? Should I create a single ISession for my whole application; an ISession for each of my forms (the application is single-threaded MDI); or an ISession for every DB operation/transaction? Does NHibernate offer some kind of built-in dirty tracking or must I do this myself? The manual mentions something like it here and there but does not go into details. How is this done? Is there not a huge overhead? Is it somehow tied with the cache(s) that NHibernate has? What are these caches for? Are they not specific to a single ISession? That is, if I use a seperate ISession for every transaction, won't it break the dirty tracking? How does the built-in dirty tracking detect deleted objects?

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• Access is denied

  - by Lasse Gaardsholt

  Hi, I got this code for my sharepoint, but I get a Access is Denied, can anyone help me out here ? <!-- Load and display list - iframe version --> <!-- Questions and comments: [email protected] --> <DIV id="ListPlaceholder"><IMG src="/_layouts/images/GEARS_AN.GIF"></DIV> <!-- Paste the URL of the source list below: --> <iframe id="SourceList" style="display:none;" src="xXxXxX" onload="DisplayThisList()"></iframe> <script type="text/javascript"> function DisplayThisList() { var placeholder = document.getElementById("ListPlaceholder"); var displaylist = null; var sourcelist = document.getElementById("SourceList"); try { if(sourcelist.contentWindow) // Internet Explorer { displaylist = sourcelist.contentWindow.document.getElementById("WebPartWPQ1") ; } } catch(err) { alert(err.message); } displaylist.removeChild(displaylist.getElementsByTagName("table")[0]); placeholder.innerHTML = displaylist.innerHTML; } </script>

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• Windows Workflow Foundation: Recommendations how to design architecture

  - by Petr Felzmann

  We are running several the same ASP.NET applications (one per customer) based on our custom framework (libraries). Each application use its own database (Initial Catalog in the term of connection string). Now we would like to add workflow capability (of course 4.0 ;) to the applications. So the particular workflows will be the same for all the applications only some initial settings of each workflow can vary, e.g. in one application the e-mail will be send to the user X, but in other application to the user Y. I have several general questions how to design architecture: (1) Can be the workflow database shared for all the applications? (2) Where to host workflow engine - inside our custom windows NT service or inside IIS? What are the criteria to choose the right host? (3) How the workflow engine should communicate with applications? Should application call some WCF endpoint API configured in workflow host or vice verse - should each application provide WCF endpoint API and workflow engine will call it? How then the workflow engine will identify applications? Both cases requires probably some application identifier as a parameter in API calls? (4) We would like to also store some information to the application databases based on the workflow states. Is it possible? Thanks for suggestions!

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• Method that does conditional return of method calling it?

  - by Mattias Konradsson

  Ok this might be a bit of hack but bear with me :) The background is that i'm tired of methods that that some if-statement to that messes up indention for the whole method, like: public SomeClass DoStuff(string inputStr) { SomeClass result =null; if (IsOpenFilter(inputStr)) { .... } return result; } So I was thinking , wouldn't it be neat if I could do something like this instead: public SomeClass DoStuff(string inputStr) { Require(IsOpenFilter(inputStr),null); .... return result; } The idea is that if the statement does not evaluates to true it would return null. If there wasn't a return type for the method it would simply be: Require(IsOpenFilter(inputStr)); I realize that this is kinda overlapping with code contracts but these would be more like "conditional" or "soft" contracts evaluated at runtime rather than compile time. So I guess there's two questions, can this be done somehow? I'm stumped on how to do a conditional return from calling a method. The other question is, is this a good idea? It's a bit weird to monkeypatch the language like this but I'd rather like the way the code reads. I would be even cleaner if it could be put into an attribute above the method: [Require(IsOpenFilter(inputStr))]

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• What IDE setup and workflow is used for OSGi development?

  - by Falx

  I made quite a few easy OSGi test projects in Eclipse RCP. My typical workflow would always be: Make 3 different projects: APIproject, Clientproject and Serverproject Edit the MANIFEST.MF of APIproject to export the api package Edit the MANIFEST.MF file of Clientproject and Serverproject to add the required API package Choose "Run as..." "Plugin Framework" OSGi console starts in eclipse and everything seems to work I also tried wiring things by using Declarative Services, which worked well like this too. Now recently I wanted to try out iPOJO. The problem is that I get the feeling that I've been doing my OSGi development the wrong way. Can it be that I should instead make 1 project en make it work like no OSGi is involved. And then afterwards, just export each package to its own bundle by means of (for instance) the BNDL tool? Should development be done in a normal Eclipse (java, not RCP) or any other java IDE for that matter? So that's why I have these questions: What IDE setup is normally used to develop OSGi with iPOJO? And what is the normal workflow to be used when developing OSGi projects (maybe with iPOJO)?

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• Question about passing data using intents

  - by Joe K 1973

  Hi everyone, I'm trying to modify the Notepad tutorial (the Notepadv3 solution) to take in a value into the NoteEdit class, given to by the Notepadv3 class. I've successfully used .putExtra in the OnListItemClick method to place the value into the NoteEdit class, but I'm struggling to do this for the createNote method; I'm getting a force close when I try to create a new note. I bet there's a simple solution, but I'm pretty new to Java & Android and would very much appreciate your help. Here's the code in question in the Notepadv3 class: private void createNote() { Intent i = new Intent(this, NoteEdit.class); i.putExtra("key", 1); startActivityForResult(i, ACTIVITY_CREATE); } @Override protected void onListItemClick(ListView l, View v, int position, long id) { super.onListItemClick(l, v, position, id); Intent i = new Intent(this, NoteEdit.class); i.putExtra(NotesDbAdapter.KEY_ROWID, id); i.putExtra("key", 1); startActivityForResult(i, ACTIVITY_EDIT); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent intent) { super.onActivityResult(requestCode, resultCode, intent); fillData(); } And here's the receiving code in the NoteEdit class: mRowId = savedInstanceState != null ? savedInstanceState.getLong(NotesDbAdapter.KEY_ROWID) : null; if (mRowId == null) { Bundle extras = getIntent().getExtras(); mRowId = extras != null ? extras.getLong(NotesDbAdapter.KEY_ROWID) : null; value = extras.getInt("key"); } I'm fairly sure that (mRowId == null) is not true when I'm using the createNote method so therefore getExtras won't be called. One of my questions would be how can I make my NoteEdit class get this value when I use the createNote method? I'm new to this so sorry if this is a simple question for you all. Thanks, Joe

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• how do i execute a stored procedure with vici coolstorage?

  - by lincolnk

  I'm building an app around Vici Coolstorage (asp.net version). I have my classes created and mapped to my database tables and can pull a list of all records fine. I've written a stored procedure where the query jumps across databases that aren't mapped with Coolstorage, however, the fields in the query result map directly to one of my classes. The procedure takes 1 parameter. so 2 questions here: how do i execute the stored procedure? i'm doing this CSParameterCollection collection = new CSParameterCollection(); collection.Add("@id", id); var result = Vici.CoolStorage.CSDatabase.RunQuery("procedurename", collection); and getting the exception "Incorrect syntax near 'procedurename'." (i'm guessing this is because it's trying to execute it as text rather than a procedure?) and also, since the class representing my table is defined as abstract, how do i specify that result should create a list of MyTable objects instead of generic or dynamic or whatever objects? if i try Vici.CoolStorage.CSDatabase.RunQuery<MyTable>(...) the compiler yells at me for it being an abstract class.

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• Class Plugins in PHP?

  - by YuriKolovsky

  i just got some more questions while learning PHP, does php implement any built in plugin system? so the plugin would be able to change the behavior of the core component. for example something like this works: include 'core.class.php'; include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; where core.class.php contains class core { public function coremethod1(){ echo 'coremethod1'; } public function coremethod2(){ echo 'coremethod2'; } } plugin1.class.php contains class plugin1 extends core { public function coremethod1(){ echo 'plugin1method1'; } } plugin2.class.php contains class plugin2 extends plugin1 { public function coremethod2(){ echo 'plugin2method2'; } } This would be ideal, if not for the problem that now the plugins are dependable on each other, and removing one of the plugins: include 'core.class.php'; //include 'plugin1.class.php'; include 'plugin2.class.php'; new plugin2; breaks the whole thing... are there any proper methods to doing this? if there are not, them i might consider moving to a different langauge that supports this... thanks for any help.

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• Beginner's guide for rails

  - by piemesons

  Hello friends i need a book/ tutorials for rails without using scoffold. All the books mentioned in the other questions are creating some depot application or etc using scaffold and then explaining things. I believe in the thing that creating big depot is worthless when you are not getting anything. All of my frnds are suggesting me to go for this pragmatic book. look i understand the book is good but i m not getting the proper things. I got the logic cause i m good in php doctrine. asp.net c c++ so i m getting the things but i m not feeling confident. I want to have a another book. Can anybody suggest me some other books. I m saying this cause it really feels good when u create a simple form and insert the values in db and u can retreive those values and MOST IMP you can explain the whole logic of the that small form application instaed of that colorfull Depot application in which things are done with scaffold and u r not getting the thing and u are confused abt the real picture.

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• svn dev cycle. howto lots minor "features" pending for approval.

  - by Julian Davchev

  Hi I've read similar questions regarding that but still feel the need to ask a question. I have scenario where we have lots of tiny "features" pending for approval. I generally see two approaches. 1.Keep trunk solid and have tons of branches for each tiny "feature". Basically every new thingy is a branch. Cons: - Might become nightmare to support so many branches no matter how small a change. Keeping all branches in sync etc etc. - Worst con I see in this is setup of test system so one can easily examine changes to approve (basically need to support all branches which seems insane). Pros: - Seemningly easy once approved a branch to be merged back to trunk and new release to be tagged and deployed. 2.For big features a branch is released and for small changes all goes in trunk(relatively stable) directly. Pros: - Easier to set test system as most of the time all will be directly visible. For big features should be easy to maintain separate branch on test. Cons: - Don't really see how release will go. I will not be able to basically release one part of trunk This would involve cherrypicking which is crazy to follow. Other approach is I just enforce that after some time (a week or so) all small features need to be approved so they can deployed before giving new tasks. I just create release branch and either all or none of small features are going live. This will be some fun discussion with head people. I guess having lots of small pending stuff is very problematic to follow technically.

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• Optimal two variable linear regression SQL statement (censoring outliers)

  - by Dave Jarvis

  Problem Am looking to apply the y = mx + b equation (where m is SLOPE, b is INTERCEPT) to a data set, which is retrieved as shown in the SQL code. The values from the (MySQL) query are: SLOPE = 0.0276653965651912 INTERCEPT = -57.2338357550468 SQL Code SELECT ((sum(t.YEAR) * sum(t.AMOUNT)) - (count(1) * sum(t.YEAR * t.AMOUNT))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as SLOPE, ((sum( t.YEAR ) * sum( t.YEAR * t.AMOUNT )) - (sum( t.AMOUNT ) * sum(power(t.YEAR, 2)))) / (power(sum(t.YEAR), 2) - count(1) * sum(power(t.YEAR, 2))) as INTERCEPT FROM (SELECT D.AMOUNT, Y.YEAR FROM CITY C, STATION S, YEAR_REF Y, MONTH_REF M, DAILY D WHERE -- For a specific city ... -- C.ID = 8590 AND -- Find all the stations within a 15 unit radius ... -- SQRT( POW( C.LATITUDE - S.LATITUDE, 2 ) + POW( C.LONGITUDE - S.LONGITUDE, 2 ) ) <15 AND -- Gather all known years for that station ... -- S.STATION_DISTRICT_ID = Y.STATION_DISTRICT_ID AND -- The data before 1900 is shaky; insufficient after 2009. -- Y.YEAR BETWEEN 1900 AND 2009 AND -- Filtered by all known months ... -- M.YEAR_REF_ID = Y.ID AND -- Whittled down by category ... -- M.CATEGORY_ID = '001' AND -- Into the valid daily climate data. -- M.ID = D.MONTH_REF_ID AND D.DAILY_FLAG_ID <> 'M' GROUP BY Y.YEAR ORDER BY Y.YEAR ) t Data The data is visualized here (with five outliers highlighted): Questions How do I return the y value against all rows without repeating the same query to collect and collate the data? That is, how do I "reuse" the list of t values? How would you change the query to eliminate outliers (at an 85% confidence interval)? The following results (to calculate the start and end points of the line) appear incorrect. Why are the results off by ~10 degrees (e.g., outliers skewing the data)? (1900 * 0.0276653965651912) + (-57.2338357550468) = -4.66958228 (2009 * 0.0276653965651912) + (-57.2338357550468) = -1.65405406 I would have expected the 1900 result to be around 10 (not -4.67) and the 2009 result to be around 11.50 (not -1.65). Thank you!

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