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  • What data structures and algorithms are applied within data warehouse cubes?

    - by Jeff Meatball Yang
    I understand that cubes are optimized data structures for aggregating and "slicing" large amounts of data. I just don't know how they are implemented. I can imagine a lot of this technology is proprietary, but are there any resources that I could use to start implementing my own cube technology? Set theory and lots of math are probably involved (and welcome as suggestions!), but I'm primarily interested in implementations: the data structures and query algorithms. Thanks!

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  • How do I get the value of a DynamicControl?

    - by Telos
    I'm using ASP.NET Dynamic Data functionality to do something a little weird. Namely, create a dynamic list of fields as children of the main object. So basically I have Ticket.Fields. The main page lists all the fields for Ticket, and the Fields property has a DynamicControl that generates a list of controls to collect more data. The tricky part is that this list ALSO uses Dynamic Data to generate the controls, so each field can be any of the defined FieldTemplates... meaning I don't necessarily know what the actual data control will be when I try to get the value. So, how do I get the value of a DynamicControl? Do I need to create a new subclass of FieldTemplate that provides a means to get at the value?

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  • Android App Widget: Data storage

    - by Jeffrey
    Hello everyone, I'm implementing a home screen app widget. I was wondering which is better to store/read data: SharedPreferences or a SQLite database? The data is accessed from an AppWidgetProvider (similar to a BroadcastReceiver), and any given instance of the widget displays different data based on appWidgetId. Is one way or the other frowned upon? Thanks for your time.

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  • Sending html data via $post fails

    - by Neil
    I am using the code below which is fine but when I use the code below that in an attempt to send an html fragment to a processing page to save it as a file but I get nothing. I have tried using ajax with processData set to false ads dataTypes of html, text and xml but nothing works. I can't find anything on this so I guess I must be missing something fairly trivial but I've been at it for 3 hours now. This works $.post("SaveFile.aspx", {f: "test4.htm", c: "This is a test"}, function(data){ alert(data); }, "text"); This fails $.post("SaveFile.aspx", {f: "test4.htm", c: "<h1>This is a test</h1>"}, function(data){ alert(data); }, "text");

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  • Reimplementing data structures in the real world

    - by Jason
    The topic of algorithms class today was reimplementing data structures, specifically ArrayList in Java. The fact that you can customize a structure for in various ways definitely got me interested, particularly with variations of add() & iterator.remove() methods. But is reimplementing and customizing a data structure something that is of more interest to the academics vs the real-world programmers? Has anyone reimplemented their own version of a data structure in a commercial application/program, and why did you pick that route over your particular language's implementation?

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  • Core Data Null Relationship

    - by Dylan Copeland
    I have a to-one relationship in my data model with Core Data. I'm trying to set the value of the relationship but Core Data keeps thinking that it's nil. The "creatorUser" relationship is not optional, so when I go to save my managed object context, Core Data gives errors because it thinks the "creatorUser" is nil. Any help would be greatly advised. NSManagedObject *teamManagedObject = [NSEntityDescription insertNewObjectForEntityForName:@"DCTeam" inManagedObjectContext:_managedObjectContext]; // Creator Properties NSManagedObject *creator = [self userForID:[ticketInfo objectForKey:@"userid"]]; if (!creator) { creator = [NSEntityDescription insertNewObjectForEntityForName:@"DCUser" inManagedObjectContext:_managedObjectContext]; [creator setValue:[personInfo objectForKey:@"userid"] forKey:@"userid"]; [creator setValue:[personInfo objectForKey:@"creatorName"] forKey:@"name"]; } [teamManagedObject setValue:creator forKey:@"creatorUser"];

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  • Elegant way of parsing Data files for Simulation

    - by sc_ray
    I am working on this project where I need to read in a lot of data from .dat files and use the data to perform simulations. The data in my .dat file looks as follows: DeviceID InteractingDeviceID InteractionStartTime InteractionEndTime 1 2 1101 1105 1,2 1101 and 1105 are tab delimited and it means Device 1 interacted with Device 2 at 1101 ms and ended the interaction at 1105ms. I have a trace data sets that compile thousands of such interactions and my job is to analyze these interactions. The first step is to parse the file. The language of choice is C++. The approach I was thinking of taking was to read the file, for every line that's read create a Device Object. This Device object will contain the property DeviceId and an array/vector of structs, that will contain a list of all the devices the given DeviceId interacted with over the course of the simulation.The struct will contain the Interacting Device Id, Interaction Start Time and Interaction End Time. I have a two fold question here: Is my approach correct? If I am on the right track, how do I rapidly parse these tab delimited data files and create Device objects without excessive memory overhead using C++? A push in the right direction will be much appreciated. Thanks

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  • Finding the most common values from given data

    - by Ben Shelock
    I have some data that looks something like this... +----------+----------+----------+ | Column 1 | Column 2 | Column 3 | +----------+----------+----------+ | Red | Blue | Green | | Yellow | Blue | Pink | | Black | Grey | Blue | +--------------------------------+ I need to go through this data and find the 3 most common colours. The raw data is in CSV and there's likely to be thousands more rows. (link) What's the best way of doing this?

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  • List of generic algorithms and data structures

    - by Jake Petroules
    As part of a library project, I want to include a plethora of generic algorithms and data structures. This includes algorithms for searching and sorting, data structures like linked lists and binary trees, path-finding algorithms like A*... the works. Basically, any generic algorithm or data structure you can think of that you think might be useful in such a library, please post or add it to the list. Thanks! (NOTE: Because there is no single right answer I've of course placed this in community wiki... and also, please don't suggest algorithms which are too specialized to be provided by a generic library) The List: Data structures AVL tree B-tree B*-tree B+-tree Binary tree Binary heap Binary search tree Linked lists Singly linked list Doubly linked list Stack Queue Sorting algorithms Binary tree sort Bubble sort Heapsort Insertion sort Merge sort Quicksort Selection sort Searching algorithms

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  • Deploying App With Dummy/Initial Data

    - by mattmccomb
    I have a Core Data based application that stores hierarchal data displayed using a series of UITableViews. To illustrate my app functionality to the user I would like to pre-populate my database/app with some dummy values. This data would be available upon installation on the user's iPhone/iPod Touch. What is the best way to achieve this?

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  • How to add database layer in core data application

    - by aditya
    Hi all I am fairly new to core data technology and i searched a lot on how to add the database to a core data application.so can anybody guide me on how to integrate the database layer? i have seen the iphone tutorial on core data (i.e books example) but i am not able to understand how to .sqlite file has been included in that application

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  • WPF/.NET data access models - resource recommendations

    - by jasonk
    We're in the early design/prep phases of transferring/updating a rather large "legacy" 3 tier client-server app to a new version. We’re looking at doing WPF over Winforms as it appears to be the direction Microsoft is pushing development of the future and we’d like the maximize the life cycle/span of the apps. That said during the rewrite we’d like to make as many changes to our data access/presentation model to improve performance as much as possible up front as many. I’ve been doing some research along that vein but the vast majority of the resources I've found that discuss WPF focus only simple data tracking apps or focus on the very basics UI design/controls. The few items that even discuss data presentation are fairly elementary in depth. Are there any books/articles/recommended reading/other resources recommended for development related to large enterprise level business apps? Any “gotchas” that should/could be avoided? General advice to minimize the time underwater

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  • Import data from .xls File

    - by tek3
    HI, I am developing an application in which i have to get data from .xls file. I am fairly new to iPhone development so any pointers in direction to getting started will be very much helpful. The steps that i am thinking are : 1) First i need to convert .xls to .csv Format. 2)Import the data from .csv file to SQlite Databse or Core Data.(I am not familier with any one of them, so kindly suggest which one to choose. I am looking forward to use Core Data) Am I thinking in the right direction. Will be greatful for any kind of assistance.. Thanx in advance..

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  • MySQL ALTER TABLE on very large table - is it safe to run it?

    - by Timothy Mifsud
    I have a MySQL database with one particular MyISAM table of above 4 million rows. I update this table about once a week with about 2000 new rows. After updating, I then perform the following statement: ALTER TABLE x ORDER BY PK DESC i.e. I order the table in question by the primary key field in descending order. This has not given me any problems on my development machine (Windows with 3GB memory), but, even though 3 times I have tried it successfully on the production Linux server (with 512MB RAM - and achieving the resulted sorted table in about 6 minutes each time), the last time I tried it I had to stop the query after about 30 minutes and rebuild the database from a backup. I have started to wonder whether a 512MB server can cope with that statement (on such a large table) as I have read that a temporary table is created to perform the ALTER TABLE command?! And, if it can be safely run, what should be the expected time for the alteration of the table? Thanks in advance, Tim

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  • Data munging and data import scripting

    - by morpheous
    I need to write some scripts to carry out some tasks on my server (running Ubuntu server 8.04 TLS). The tasks are to be run periodically, so I will be running the scripts as cron jobs. I have divided the tasks into "group A" and "group B" - because (in my mind at least), they are a bit different. Task Group A import data from a file and possibly reformat it - by reformatting, I mean doing things like santizing the data, possibly normalizing it and or running calculations on 'columns' of the data Import the munged data into a database. For now, I am mostly using mySQL for the vast majority of imports - although some files will be imported into a sqlLite database. Note: The files will be mostly text files, although some of the files are in a binary format (my own proprietary format, written by a C++ application I developed). Task Group B Extract data from the database Perform calculations on the data and either insert or update tables in the database. My coding experience is is primarily as a C/C++ developer, although I have been using PHP as well for the last 2 years or so. I am from a windows background so I am still finding my feet in the linux environment. My question is this - I need to write scripts to perform the tasks I described above. Although I suppose I could write a few C++ applications to be used in the shell scripts, I think it may be better to write them in a scripting language (maybe this is a flawed assumption?). My thinking is that it would be easier to modify thins in a script - no need to rebuild etc for changes to functionality. Additionally, C++ data munging in C++ tends to involve more lines of code than "natural" scripting languages such as Perl, Python etc. Assuming that the majority of people on here agree that scripting is the way to go, herein lies my dilema. Which scripting language to use to perform the tasks above (giving my background). My gut instinct tells me that Perl (shudder) would be the most obvious choice for performing all of the above tasks. BUT (and that is a big BUT). The mere mention of Perl makes my toes curl, as I had a very, very bag experience with it a while back. The syntax seems quite unnatural to me - despite how many times I have tried to learn it - so if possible, I would really like to give it a miss. PHP (which I already know), also am not sure is a good candidate for scripting on the CLI (I have not seen many examples on how to do this etc - so I may be wrong). The last thing I must mention is that IF I have to learn a new language in order to do this, I cannot afford (time constraint) to spend more than a day, in learning the key commands/features required in order to do this (I can always learn the details of the language later, once I have actually deployed the scripts). So, which scripting language would you recommend (PHP, Python, Perl, [insert your favorite here]) - and most importantly WHY?. Or, should I just stick to writing little C++ applications that I call in a shell script?. Lastly, if you have suggested a scripting language, can you please show with a FEW lines (Perl mongers - I'm looking in your direction [nothing to cryptic!] ;) ) how I can use the language you suggested to do what I want to do. Hopefully, the lines you present will convince me that it can be done easily and elegantly in the language you suggested.

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  • jQuery: Use of undefined constant data assumed 'data'

    - by morpheous
    I am trying to use jQuery to make a synchronous AJAX post to a server, and get a JSON response back. I want to set a javascript variable msg upon successful return This is what my code looks like: $(document).ready(function(){ $('#test').click(function(){ alert('called!'); jQuery.ajax({ async: false, type: 'POST', url: 'http://www.example.com', data: 'id1=1&id2=2,&id3=3', dataType: 'json', success: function(data){ msg = data.msg; }, error: function(xrq, status, et){alert('foobar\'d!');} }); }); [Edit] I was accidentally mixing PHP and Javascript in my previous xode (now corrected). However, I now get this even more cryptic error message: uncaught exception: [Exception... "Component returned failure code: 0x80070057 (NS_ERROR_ILLEGAL_VALUE) [nsIXMLHttpRequest.open]" nsresult: "0x80070057 (NS_ERROR_ILLEGAL_VALUE)" location: "JS frame :: http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js :: anonymous :: line 19" data: no] What the ... ?

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  • ways to store data in c#

    - by Audel
    I am looking for ways to store data in a windows form application in C#. I want to make the input data of a system persistent, so when I close my program and open it again, the data is retrieved. Which ways are of doing this besides creating a linked database? Examples are gladly appreciated regards

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  • Handling missing/incomplete data in R

    - by doug
    As you would expect from a DSL aimed at data analysts, R handles missing/incomplete data very well, for instance: Many R functions have an 'na.rm' flag that you can set to 'T' to remove the NAs, but if you want to deal with this before the function call, then: to replace each 'NA' w/ 0: ifelse(is.na(vx), 0, vx) to remove each 'NA': vx = vx[!is.na(a)] to remove entire each row that contains 'NA' from a data frame: dfx = dfx[complete.cases(dfx),] All of these functions remove 'NA' or rows with an 'NA' in them. Sometimes this isn't quite what you want though--making an 'NA'-excised copy of the data frame might be necessary for the next step in the workflow but in subsequent steps you often want those rows back (e.g., to calculate a column-wise statistic for a column that has missing rows caused by a prior call to 'complete cases' yet that column has no 'NA' values in it). to be as clear as possible about what i'm looking for: python/numpy has a class, 'masked array', with a 'mask' method, which lets you conceal--but not remove--NAs during a function call. Is there an analogous function in R?

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  • Using R to download zipped data file, extract, and import data

    - by Jeromy Anglim
    @EZGraphs on Twitter writes: "Lots of online csvs are zipped. Is there a way to download, unzip the archive, and load the data to a data.frame using R? #Rstats" I was also trying to do this today, but ended up just downloading the zip file manually. I tried something like: fileName <- "http://www.newcl.org/data/zipfiles/a1.zip" con1 <- unz(fileName, filename="a1.dat", open = "r") but I feel as if I'm a long way off. Any thoughts?

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  • Adding a new column to Table which contains live data

    - by Ardman
    I have a large table consisting of over 60 millions records and I would like to add 2 new columns for data migration purposes. There are indexes on the table and some of them are large. So, by me adding the 2 new columns to the table, will I run the risk of slowing down the database whilst it attempts to add them and maybe time-out? Or will it just work? I know that if I try and rearrange the columns SQL Server will ask me to drop and re-create the table, so I definately don't want this. Is this something everyone is challenged with?

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  • function to find common rows between more than two data frames in R

    - by biohazard
    I have 4 data frames, and would like to find the rows whose values in a certain column do not exist in any of the other data frames. I wrote this function: #function to test presence of $Name in 3 other datasets common <- function(a, b, c, d) { is.B <- is.numeric(a$Name %in% b$Name) == 1 is.C <- is.numeric(a$Name %in% c$Name) == 1 is.D <- is.numeric(a$Name %in% d$Name) == 1 t <- as.numeric(is.B & is.C & is.D) t } However, the output is always t = 0. This means that it tells me that there are no unique rows in any data sets, even though the datas frames have very different numbers of rows. Since there are no duplicate rows in any of the data frames, I should be getting t = 1 for at least some rows in the biggest dataset. Can someone figure out what I got wrong?

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  • Detaching all entities of T to get fresh data

    - by Goran
    Lets take an example where there are two type of entites loaded: Product and Category, Product.CategoryId - Category.Id. We have available CRUD operations on products (not Categories). If on another screen Categories are updated (or from another user in the network), we would like to be able to reload the Categories, while preserving the context we currently use, since we could be in the middle of editing data, and we do not want changes to be lost (and we cannot depend on saving, since we have incomplete data). Since there is no easy way to tell EF to get fresh data (added, removed and modified), we thought of twp possible ways: 1) Getting products attached to context, and categories detached from context. This would mean that we loose the ability to access Product.Category.Name, which we do sometimes require, so we would need to manually resolve it (example when printing data). 2) detaching / attaching all Categories from current context. Context.ChangeTracker.Entries().Where(x => x.Entity.GetType() == typeof(T)).ForEach(x => x.State = EntityState.Detached); And then reload the categories, which will get fresh data. Do you find any problem with this second approach? We understand that this will require all constraints to be put on foreign keys, and not navigation properties, since when detaching all Categories, Product.Category navigation properties would be reset to null also. Also, there could be a potential performance problem, which we did not test, since there could be couple of thousand products loaded, and all would need to resolve navigation property when reloading. Which of the two do you prefer, and is there a better way (EF6 + .NET 4.0)?

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  • How to send mail with large size attachment using System.Net.Mail to Google Apps ?

    - by Preeti
    Hi, I am trying to send mail with large size attachment upto (1MB,2MB). But sending mail fails.(Sending to Google Apps) as: MailItemEntry[] entries = new MailItemEntry[1]; String EmlPath = "C:\\testemail.eml"; String msg = File.ReadAllText(EmlPath); entries[0] = new MailItemEntry(); entries[0].Rfc822Msg = new Rfc822MsgElement(msg); How can i divide attachments into multi part? Exception I am getting while migrating this EML to Google apps is: {"The request was aborted: The request was canceled."}

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  • JSON parse data in javascript from php

    - by Stefania
    I'm trying to retrieve data in a javascript file from a php file using json. $items = array(); while($r = mysql_fetch_array($result)) { $rows = array( "id_locale" => $r['id_locale'], "latitudine" => $r['lat'], "longitudine" => $r['lng'] ); array_push($items, array("item" => $rows)); } ECHO json_encode($items); and in the javascript file I try to recover the data using an ajax call: $.ajax({ type:"POST", url:"Locali.php", success:function(data){ alert("1"); //var obj = jQuery.parseJSON(idata); var json = JSON.parse(data); alert("2"); for (var i=0; i<json.length; i++) { point = new google.maps.LatLng(json[i].item.latitudine,json[i].item.longitudine); alert(point); } } }) The first alert is printed, the latter does not, it gives me error: Unexpected token <.... but I do not understand what it is. Anyone have any idea where am I wrong? I also tried to recover the data with jquery but with no positive results.

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