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  • How to reduce a data frame keeping the order for other columns

    - by betabandido
    I am trying to reduce a data frame using the max function on a given column. I would like to preserve other columns but keeping the values from the same rows where each maximum value was selected. An example will make this explanation easier. Let us assume we have the following data frame: dframe <- data.frame(list(BENCH=sort(rep(letters[1:4], 4)), CFG=rep(1:4, 4), VALUE=runif(4 * 4) )) This gives me: BENCH CFG VALUE 1 a 1 0.98828096 2 a 2 0.19630597 3 a 3 0.83539540 4 a 4 0.90988296 5 b 1 0.01191147 6 b 2 0.35164194 7 b 3 0.55094787 8 b 4 0.20744004 9 c 1 0.49864470 10 c 2 0.77845408 11 c 3 0.25278871 12 c 4 0.23440847 13 d 1 0.29795494 14 d 2 0.91766057 15 d 3 0.68044728 16 d 4 0.18448748 Now, I want to reduce the data in order to select the maximum VALUE for each different BENCH: aggregate(VALUE ~ BENCH, dframe, FUN=max) This gives me the expected result: BENCH VALUE 1 a 0.9882810 2 b 0.5509479 3 c 0.7784541 4 d 0.9176606 Next, I tried to preserve other columns: aggregate(cbind(VALUE, CFG) ~ BENCH, dframe, FUN=max) This reduction returns: BENCH VALUE CFG 1 a 0.9882810 4 2 b 0.5509479 4 3 c 0.7784541 4 4 d 0.9176606 4 Both VALUE and CFG are reduced using max function. But this is not what I want. For instance, in this example I would like to obtain: BENCH VALUE CFG 1 a 0.9882810 1 2 b 0.5509479 3 3 c 0.7784541 2 4 d 0.9176606 2 where CFG is not reduced, but it just keeps the value associated to the maximum VALUE for each different BENCH. How could I change my reduction in order to obtain the last result shown?

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  • Quickly generate junk data of certain size in Javascript

    - by user1357607
    I am writing an upload speed test in Javascript. I am using Jquery (and Ajax) to send chunks of data to a server in order to time how long it takes to get a response. This should, in theory give an estimation, of the upload speed. Of course to cater for different bandwidths of the user I sequentially upload larger and larger amounts of junk data until a threshold duration is reached. Currently I generate the junk data using the following function, however, it is very slow when generation megabytes of data. function generate_random_data(size){ var chars = "abcdefghijklmnopqrstuvwxyz"; var random_data = ""; for (var i = 0; i < size; i++){ var random_num = Math.floor(Math.random() * char.length); random_data = random_data + chars.substring(random_num,random_num+1); } return random_data; Really all I am doing is generating a chunk of bytes to send to the server, however, this is the only way I could find out how in Javascript. Any help would be appreciated.

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  • Data transformation question

    - by tkm
    I have data composed of a list of employers and a list of workers. Each has a many-to-many relationship with the other (so an employer can have many workers, and a worker can have many employers). The way the data is retrieved (and given to me) is as follows: each employer has an array of workers. In other words: employer n has: worker x, worker y etc. So I have a bunch of employer objects each containing an array of workers. I need to transform this data (and basically invert the relationship). I need to have a bunch of worker objects, each containing and array of employers. In other words: worker x has: employer n1, employer n2 etc. The context is hypothetical so please don't comment on why I need this or why I am doing it this way. I would really just like help on the algorithm to perform this transformation (there isn't that much data so I would prefer readability over complex optimizations which reduce complexity). (Oh and I am using Java, but pseudocode would be fine). Thanks!

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  • Is adding users to the group www-data safe on Debian?

    - by John
    Many PHP applications do self-configuration and self-updating. This requires apache to have write access to the PHP files. While chgrp'ing them all to www-data appears like a good practice to avoid making them world writable, I also wish to allow users to create new files and edit existing one. Is adding users to the group www-data safe on Debian? For example: 775 root www-data /var/www 644 john www-data /var/www/johns_php_application.php 660 john www-data /var/www/johns_php_applications_configuration_file

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  • Problems with data driven testing in MSTest

    - by severj3
    Hello, I am trying to get data driven testing to work in C# with MSTest/Selenium. Here is a sample of some of my code trying to set it up: [TestClass] public class NewTest { private ISelenium selenium; private StringBuilder verificationErrors; [DeploymentItem("GoogleTestData.xls")] [DataSource("System.Data.OleDb", "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=GoogleTestData.xls;Persist Security Info=False;Extended Properties='Excel 8.0'", "TestSearches$", DataAccessMethod.Sequential)] [TestMethod] public void GoogleTest() { selenium = new DefaultSelenium("localhost", 4444, "*iehta", http://www.google.com); selenium.Start(); verificationErrors = new StringBuilder(); var searchingTerm = TestContext.DataRow["SearchingString"].ToString(); var expectedResult = TestContext.DataRow["ExpectedTextResults"].ToString(); Here's my error: Error 3 An object reference is required for the non-static field, method, or property 'Microsoft.VisualStudio.TestTools.UnitTesting.TestContext.DataRow.get' E:\Projects\SeleniumProject\SeleniumProject\MaverickTest.cs 32 33 SeleniumProject The error is underlining the "TestContext.DataRow" part of both statements. I've really been struggling with this one, thanks!

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  • RIA Services vs ADO.NET Data Services

    - by Cody C
    I'm currently in the process of creating a Silverlight 3 data driven application. To access the database, 2 common approaches are used: RIA Services and ADO.NET Data Services. Does anyone have any guidance on when/why to choose each approach? Here is what I've gathered from my research / experience. Any thoughts? ADO.NET seems to be only useful for strictly database calls. If you need to expose the data services to other applications (ignoring Silverlight 3's domain restriction), this is a good approach. Also, if the URL/Query syntax can be useful in your application, this is another advantage RIA Services seem to be a more flexible, accepted framework. It seems to give you more than strictly database access. It does have a limitation of only being used for the Silverlight / Web application as it is not exposed via a service. Thoughts? Ideas? Comments?

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  • Stack data storage order

    - by Jamie Dixon
    When talking about a stack in either computing or "real" life we usually assume a "first on, last off" type of functionality. Because the idea of a stack is based around something in the physical world, does it matter how the data in the stack is stored? I notice in a lot of examples that the storage of the stack data is quite often done using an array and the newest item added to the stack is placed at the bottom of the array. (like adding a new plate to an existing stack of plates except putting it underneath the other plates rather than on top). As a paradigm, does it matter in what order the data is stored within the stack as long as the operation of the stack acts as expected?

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  • asp.NET Dynamic Data Site and asp.NET MVC-2 site together

    - by loviji
    Hi, I have created firstly ASP.NET MVC 2. and write more functionality. After I create asp.NET Dynamic Data Site. now, when I click on run button in Visual Studio, mvc app. opened in browser as http://localhost:50062. and asp.NET Dynamic Data Site as http://localhost:58395/cms/. but i want to merge this app. in one. can I use asp.NET Dynamic Data Site and asp.NET MVC-2 at the same time?

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  • WCF Data Services consuming data from EF based repository

    - by John Kattenhorn
    We have an existing repository which is based on EF4 / POCO and is working well. We want to add a service layer using WCF Data Services and looking for some best practice advice. So far we have developed a class which has a IQueryable property and the getter triggers the repository 'get all users' method. The problem so far have been two-fold: 1) It required us to decorate the ID field of the poco object to tell data service what field was the id. This now means that our POCO object is not 'pure'. 2) It cannot figure out the relationships between the objects (which is obvious i guess). I've now stopped this approach and i'm thinking that maybe we should expose the OBjectContext from the repository and use more 'automatic' functionality of EF. Has anybody got any advice or examples of using the repository pattern with WCF Data Services ?

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  • ETL Operation - Return Primary Key

    - by user302254
    I am using Talend to populate a data warehouse. My job is writing customer data to a dimension table and transaction data to the fact table. The surrogate key (p_key) on the fact table is auto-incrementing. When I insert a new customer, I need my fact table to reflect the id of the related customer. As I mentioned my p_key is auto auto_incrementing so I can't just insert an arbitrary value for the p_key. Any thought on how I can insert a row into my dimension table and still retrieve the primary key to reference in my fact record? Thanks.

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  • best way to save data in ipod touch/iphone objective-c

    - by Leonardo
    Hi all, I am writing a very simple application, for iphone. Unfortunately I am really a newbie. What I am trying to do is to save data at the end of a user experience. These data are really simple, only string or int, or some array. Later I want to be able to retrieve that data, therefore I also need an event id (I suppose). Could you please point out the best way, api or technology to achieve that, xml, plain text, serialization... ? many thanks Leonardo

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  • Messaging Systems – Handshaking, Reconciliation and Tracking for Data Transparency

    - by Ahsan Alam
    As many corporations build business partnerships with other organizations, the need to share information becomes necessary. Large amount of data sharing using snail mail, email and/or fax are quickly becoming a thing of the past. More and more organizations are relying heavily on Ftp and/or Web Service to exchange data. Corporations apply wide range of technologies and techniques based on available resources and data transfer needs. Sometimes, it involves simple home-grown applications. Other times, large investments are made on products like BizTalk, TIBCO etc. Complexity of information management also varies significantly from one organizations to another. Some may deal with handful of simple steps to process and manage shared data; whereas others may rely on fairly complex processes with heavy interaction with internal and external systems in order to serve the business needs. It is not surprising that many of these systems end up becoming black boxes over a period of time. Consequently, people and business start to rely more and more on developers and support personnel just to extract simple information adding to the loss of productivity. One of the most important factor in any business is transparency to data irrespective of technology preferences and the complexity of business processes. Not knowing the state of data could become very costly to the business. Being involved in messaging systems for some time now, I have heard the same type of questions over and over again. Did we transmit messages successfully? Did we get responses back? What is the expected turn-around-time? Did the system experience any errors? When one company transmits data to one or more company, it may invoke a set of processes that could complete in matter of seconds, or it could days. As data travels from one organizations to another, the uncertainty grows, and the longer it takes to track uncertain state of the data the costlier it gets for the business, So, in every business scenario, it's extremely important to be aware of the state of the data.   Architects of messaging systems can take several steps to aid with data transparency. Some forms of data handshaking and reconciliation mechanism as well as extensive data tracking can be incorporated into the system to provide clear visibility to the data. What do I mean by handshaking and reconciliation? Some might consider these to be a single concept; however, I like to consider them in two unique categories. Handshaking serves as message receipts or acknowledgment. When one transmits messages to another, the receiver must acknowledge each message by sending immediate responses for each transaction. Whenever we use Web Services, handshaking is often achieved utilizing request/reply pattern. Similarly, if Ftp is used, a receiver can acknowledge by dropping messages for the sender as soon as the files are picked up. These forms of handshaking or acknowledgment informs the message sender and receiver that a successful transaction has occurred. I have mentioned earlier that it could take anywhere from a few seconds to a number of days before shared data is completely processed. In addition, whenever a batched transaction is used, processing time for each data element inside the batch could also vary significantly. So, in order to successfully manage data processing, reconciliation becomes extremely important; otherwise it may result into data loss or in some cases hefty penalty. Reconciliation can be done in many ways. Partner organizations can share and compare ad hoc reports to achieve reconciliation. On the other hand, partners can agree on some type of systematic reconciliation messages. Systems within responsible parties can trigger messages to partners as soon as the data process completes.   Next step in the data transparency is extensive data tracking. Some products such as BizTalk and TIBCO provide built-in functionality for data tracking; however, built-in functionality may not always be adequate. Sometimes additional tracking system (or databases) needs to be built in order monitor all types of data flow including, message transactions, handshaking, reconciliation, system errors and many more. If these types of data are captured, then these can be presented to business users in any forms or fashion. When business users are empowered with such information, then the reliance on developers and support teams decreases dramatically.   In today's collaborative world of information sharing, data transparency is key to the success of every business. The state of business data will constantly change. However, when people have easier access to various states of data, it allows them to make better and quicker decisions. Therefore, I feel that data handshaking, reconciliation and tracking is very important aspect of messaging systems.

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  • iphone tab bar controller and core data.

    - by Sway
    Ok bit of a newbie type question. I want to use Core Data, together with Tab and Navigation controllers. In XCode if I create a Navigation Based Application I get the option to choose Core Data. Whereas If I create a Tab Bar Application I don't get the choice. I understand that Tab Bars display view controllers so it kinda makes sense. However given that by default it sticks the basic Core Data code in the Application delegate I don't see why this isn't offered. At the moment I'm creating the two projects and cutting and pasting between them. Does this omission in XCode seem weird to you? Is it some sort of oversight? Thanks, Matt

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  • Seed data for grails application

    - by bsreekanth
    Hello, What is the best way to load seed (initial or test) data into grails application. I'm considering 3 options 1. Putting everything in *BootStrap.groovy files. This is tedious if the domain classes and test data are many. 2. Write custom functionality to load it through xml. May not be too difficult with the excellent xml support by groovy, but lot of switch statements for different domain classes. 3. Use Liquibase LoadData api. I see you can load the data fairly easy from csv files. Choice 3 seems the easiest. But, I'm not familiar with Liquibase. Is it good in this scenario, or only used for migration, db changes etc. If anyone could provide a better sol, or point to an example with Liquibase, it would be great help.. thanks...

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  • Automating scraping of table data to XML

    - by thewinchester
    Problem I have a YQL query result that I'm trying to get converted and sort into a clean XML file. Background Being the pains that they are, information from the World Cup isn't freely available in an easy to reuse format. So, after a bit of finessing with YQL I have managed to liberate the required table rows which contain the data I'm after. The YQL query can be viewed at: http://query.yahooapis.com/v1/public/yql/ravingbeefsteak/worldcup2010groupliberator?diagnostics=true I'd like to now convert this information into XML, and being an absolute n00b I don't know where to start or what to look for. I'm also needing to do a find and replace on the data to get the URL's working as they should without manual changes, and hopefully an initial sorting of the data. If anyone can point me in the right direction of what I need to be doing to make my needs a reality it would be greatly appreciated.

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  • Sorting NSSets of a core data entity - Objective-c

    - by ncohen
    Hi everyone, I would like to sort the data of a core data NSSet (I know we can do it only with arrays but let me explain...). I have an entity user who has a relationship to-many with the entity recipe. A recipe has the attributes name and id. I would like to get the data such that: Code: NSArray *id = [[user.recipes valueForKey:@"identity"] allObjects]; NSArray *name = [[user.recipes valueForKey:@"name"] allObjects]; if I take the object at index 1 in both arrays, they correspond to the same recipe... Thanks

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  • How to persist a very abstract data type between sessions: PHP

    - by Greelmo
    I have an abstract data type that behaves much like stack. It represents a history of "graph objects" made by a particular user. Each "graph object" holds one or more "lines", a date range, keys, and a title. Each "line" holds a sql generator configured for a particular subset of data in my db. I would like for these "histories" to be available to users between their sessions. It will be in the form of a tab that reads something like "most recent graphs". What do you believe to be the best way to persist this type of data between sessions. This application could get rather large, so efficiency is a concern. Thanks in advance.

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  • Protecting Data Feed for iPhone App

    - by Chris
    I am creating an App that pulls data from a file on my server. That file gets data from my database, based on GET values that are passed through the URL. I would like to keep this feed closed - that is, I don't want people finding the datasource and reading the data on their own. I considered sending an alphanumeric id along with the url string, but if they can find the URL that I am calling, then there won't be anything preventing them from grabbing that alphanumeric id also. I am looking for any ideas or experiences that might help me here. Thanks.

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  • Suggest Cassandra data model for an existing schema

    - by Andriy Bohdan
    Hello guys! I hope there's someone who can help me suggest a suitable data model to be implemented using nosql database Apache Cassandra. More of than I need it to work under high loads and large amounts of data. Simplified I have 3 types of objects: Product Tag ProductTag Product: key - string key name - string .... - some other fields Tag: key - string key name - unique tag words ProductTag: product_key - foreign key referring to product tag_key - foreign key referring to tag rating - this is rating of tag for this product Each product may have 0 or many tags. Tag may be assigned to 1 or many products. Means relation between products and tags is many-to-many in terms of relational databases. Value of "rating" is updated "very" often. I need to be run the following queries Select objects by keys Select tags for product ordered by rating Select products by tag order by rating Update rating by product_key and tag_key The most important is to make these queries really fast on large amounts of data, considering that rating is constantly updated.

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  • Interpolation of scattered data: What could I do?

    - by Simon
    Hi! I need your help. I'm working on a 3D chart in Java using Java 3D. It should be able to display a bunch of measured values. As measured, the data I get is scattered. This means I will have to interpolate the missing points in order to get my surface plotted nicely. I didn't study all that 3D-Geometry stuff yet and I don't know where to start. My idea is to triangulate the points to a surface and then, based on the triangulation, interpolate the missing points. (see this to have a rough idea of what I want to achieve) Does someone have experiences with the interpolation of scattered data? Is my approach the right one? If yes, what kind of data structures and algorithms will I need in order to triangulate my points cloud?

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  • Functional data structures in C++

    - by drg
    Does anyone know of a C++ data structure library providing functional (a.k.a. immutable, or "persistent" in the FP sense) equivalents of the familiar STL structures? By "functional" I mean that the objects themselves are immutable, while modifications to those objects return new objects sharing the same internals as the parent object where appropriate. Ideally, such a library would resemble STL, and would work well with Boost.Phoenix (caveat- I haven't actually used Phoenix, but as far as I can tell it provides many algorithms but no data structures, unless a lazily-computed change to an existing data structure counts - does it?)

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  • Core Data store corruption

    - by sehugg
    A handful of customers for my iPhone app are experiencing Core Data store corruption (I assume so, since the error is "Failed to save to data store: Operation could not be completed. (Cocoa error 259.)") Has anyone else experienced this kind of store corruption? I am worried since I aim to soon push an update which performs a schema migration, and I am worried that this will expose even more problems. I had assumed that the Core Data/SQLlite APIs use atomic operations and are immune to corruption except if the underlying filesystem experiences corruption. Is there a way to reduce/prevent corruption, or at least a good way to reproduce (I have been unsuccessful thus far).

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  • Looking for a Magnetic Card Reader with data storage

    - by Omar Sharif
    I am looking for a magnetic card reader with data storage of about 2 GB. This reader be placed in open under a shade, but would be exposed to temperatures from -5 C to 50 C. Job is to swipe customer loyalty cards issued to regular customers of a gas station. Each time they get gas filled, they will swipe their card, to mark their presence. Swiped data be stored in the reader. And on intervals be transferred to a PC lying in the office. The customer visits data be used to award some gifts or benefits to frequently visiting clients. Any ready-made solutions available ? Please advise. Omar

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  • Faking a dynamic schema in Core Data?

    - by Gouldsc
    From reading the Apple Docs on Core Data, I've learned that you should not use Core Data when you need a dynamic schema. If I wanted to provide the user the ability to create their own properties, in a core data model would it work if I created some "dummy" attributes like "custom decimal 1", "custom decimal 2", "custom text 1", "custom text 2" etc that the user could name and use for their own purposes? Obviously this won't work for relationships, but for simple properties it seems like a reasonable workaround. Will creating a bunch of dummy attributes on my entities that go unused by most users noticeably decrease performance for them? Have any of you tried something like this? Thanks!

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  • creating managed objects using code in xcode & core-data

    - by themadpeacock
    New to objective-c xcode and core-data so sorry for the remedial question. I have set up a very simple data model: Entity1 and Entity2, both contain a single attribute (String) and a one-to-many relationship with the other. I want to scan Entity1 and depending on the results of the scan create one or more Entity2 objects that link to Entity1. How can I do this? I don’t understand how I create Entity2 type objects in code and how I would define the relationship to the Entity1 object they are related to. I come from a SQL programming background where inserting elements into the Entity2 table with the ID of the related Entiry1 entry is easy. I can’t get my head around the xcode core-data abstraction and would appreciate any help.

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