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• Painless way to install a new version of R?

  - by Shane

  Andrew Gelman recently lamented the lack of an easy upgrade process for R (probably more relevant on Windows that Linux). Does anyone have a good trick for doing the upgrade, from installing the software to copying all the settings/packages over? This suggestion was contained in the comments and is what I've been using recently. First you install the new version, then run this in the old verion: #--run in the old version of R setwd("C:/Temp/") packages <- installed.packages()[,"Package"] save(packages, file="Rpackages") Followed by this in the new version: #--run in the new version setwd("C:/Temp/") load("Rpackages") for (p in setdiff(packages, installed.packages()[,"Package"])) install.packages(p)

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• urgent..haskell mini interpreter

  - by mohamed elshikh

  i'm asked to implement this project and i have problems in part b which is the eval function this is the full describtion of the project You are required to implement an interpreter for mini-Haskell language. An interpreter is dened in Wikipedia as a computer program that executes, i.e. performs, instructions written in a programming language. The interpreter should be able to evaluate functions written in a special notation, which you will dene. A function is dened by: Function name Input Parameters : dened as a list of variables. The body of the function. The body of the function can be any of the following statements: a) Variable: The function may return any of the input variables. b) Arithmetic Expressions: The arithmetic expressions include input variables and addition, sub- traction, multiplication, division and modulus operations on arithmetic expressions. c) Boolean Expressions: The Boolean expressions include the ordering of arithmetic expressions (applying the relationships: <, =<, , = or =) and the anding, oring and negation of Boolean expressions. d) If-then-else statements: where the if keyword is followed by a Boolean expression. The then and else parts may be followed by any of the statements described here. e) Guarded expressions: where each case consists of a boolean expression and any of the statements described here. The expression consists of any number of cases. The rst case whose condition is true, its body should be evaluated. The guarded expression has to terminate with an otherwise case. f) Function calls: the body of the function may have a call to another function. Note that all inputs passed to the function will be of type Int. The output of the function can be of type Int or Bool. To implement the interpreter, you are required to implement the following: a) Dene a datatype for the following expressions: Variables Arithmetic expressions Boolean expressions If-then-else statements Guarded expressions Functions b) Implement the function eval which evaluates a function. It takes 3 inputs: The name of a function to be evaluated represented as a string. A list of inputs to that function. The arguments will always be of datatype Int. A list of functions. Each function is represented as instance of the datatype that you have created for functions. c) Implement the function get_type that returns the type of the function (as a string). The input to this function is the same as in part b. here is what i've done data Variable = v(char) data Arth= va Variable | Add Arth Arth | Sub Arth Arth | Times Arth Arth | Divide Arth Arth data Bol= Great Arth Arth | Small Arth Arth | Geq Arth Arth | Seq Arth Arth | And Bol Bol | Or Bol Bol | Neg Bol data Cond = data Guard = data Fun =cons String [Variable] Body data Body= bodycons(String) |Bol |Cond |Guard |Arth

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• Scala downwards or decreasing for loop?

  - by Felix

  In scala, you often use an iterator to do a for loop in an increasing order like: for(i <- 1 to 10){ code } How would you do it so it goes from 10 to 1? I guess 10 to 1 gives an empty iterator (like usual range mathematics)? I made a scala script which solves it by calling reverse on the iterator, but it's not nice in my opinion, is this the way to go: def nBeers(n:Int) = n match { case 0 => ("No more bottles of beer on the wall, no more bottles of beer."+ "\nGo to the store and buy some more, "+ "99 bottles of beer on the wall.\n") case _ => (n+" bottles of beer on the wall, "+n +" bottles of beer.\n"+"Take one down and pass it around, "+ (if((n-1)==0) "no more" else (n-1))+ " bottles of beer on the wall.\n") } for(b <- (0 to 99).reverse)println(nBeers(b)) ?? Any comments/suggestions?

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• How to refresh a fragment in a viewpager?

  - by aut_silvia

  I know there are already some questions to this problem. But I am really new in Android and ecspecially to Fragments and Viewpager. Pls have passion with me. I didn't found a answer which fits to my code. I dont know how to refresh a fragment or reload it when it's "active" again. TabsPagerAdapter.java: public class TabsPagerAdapter extends FragmentPagerAdapter{ public TabsPagerAdapter(FragmentManager fm){ super(fm); } @Override public Fragment getItem(int index) { switch (index) { case 0: return new KFZFragment(); case 1: return new LogFragment(); case 2: return new TrackFragment(); } return null; } @Override public int getCount() { // get item count - equal to number of tabs return 3; } } I have this 3 Fragments (KFZFragment,LogFragment,TrackFragment) and on the TrackFragment I calculate some data and this data should be display in a ListView in LogFragment. But when I change to LogFragment it's not the latest data. So it doesnt refresh. Now how should I modify my code to refresh the fragments when it's "active"? MainActivityFragment.java: public class MainActivityFragment extends FragmentActivity implements ActionBar.TabListener{ private ViewPager viewPager; private TabsPagerAdapter mAdapter; private ActionBar actionBar; List<Fragment> fragments; private String[] tabs = { "KFZ", "Fahrten Log", "Kosten Track" }; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main_fragment); // Initilization viewPager = (ViewPager) findViewById(R.id.pager); actionBar = getActionBar(); mAdapter = new TabsPagerAdapter(getSupportFragmentManager()); fragments = new Vector<Fragment>(); fragments.add(Fragment.instantiate(this, KFZFragment.class.getName(),savedInstanceState)); fragments.add(Fragment.instantiate(this, LogFragment.class.getName(),savedInstanceState)); viewPager.setAdapter(mAdapter); actionBar.setHomeButtonEnabled(false); actionBar.setNavigationMode(ActionBar.NAVIGATION_MODE_TABS); // Adding Tabs for (String tab_name : tabs) { actionBar.addTab(actionBar.newTab().setText(tab_name) .setTabListener(this)); } viewPager.setOnPageChangeListener(new ViewPager.OnPageChangeListener() { @Override public void onPageSelected(int position) { // on changing the page // make respected tab selected actionBar.setSelectedNavigationItem(position); } @Override public void onPageScrolled(int arg0, float arg1, int arg2) { } @Override public void onPageScrollStateChanged(int arg0) { } }); } @Override public void onTabReselected(Tab tab, FragmentTransaction ft) { // TODO Auto-generated method stub } @Override public void onTabSelected(Tab tab, FragmentTransaction ft) { viewPager.setCurrentItem(tab.getPosition()); } @Override public void onTabUnselected(Tab tab, FragmentTransaction ft) { // TODO Auto-generated method stub } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if (keyCode == KeyEvent.KEYCODE_BACK) { } return super.onKeyDown(keyCode, event); } } Pls help me out.

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• Do timers created using timer_create go off during a getch()?

  - by flarn2006

  In case you don't know, getch() is a curses function.

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• In SQL / MySQL, what is the difference between "On" and "Where" in a join statement?

  - by Jian Lin

  The following statements give the same result (one is using "on", and the other using "where"): mysql> select * from gifts INNER JOIN sentGifts on gifts.giftID = sentGifts.giftID; mysql> select * from gifts INNER JOIN sentGifts where gifts.giftID = sentGifts.giftID; I can only see in a case of a Left Outer Join finding the "unmatched" cases: (to find out the gifts that were never sent by anybody) mysql> select name from gifts LEFT OUTER JOIN sentgifts on gifts.giftID = sentgifts.giftID where sentgifts.giftID IS NULL; In this case, it is first using "on", and then "where". Does the "on" first do the matching, and then "where" does the "secondary" filtering? Or is there a more general rule of using "on" versus "where"? Thanks.

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• How to make WPF Listview works same as Photoshop layer

  - by Youngjae

  As we can see in Photoshop layer window (or other image editting tool also), it has several features: groups with folder-like header (collapse/expandable) ungroupped item (no header) sort "manually" by dragging. In case of No 1, I made groupped item with expander control. (ref: http://www.dotnetspark.com/kb/1753-expand-and-collapse-listbox-group-header.aspx) In case of No 3, Sort manually can be solved with this code. (ref: codeproject.com/kb/WPF/ListViewDragDropManager.aspx) but I don't know how to list ungroupped items together. Of course, the ungroupped items may not have a header. I am using ICollectionView and MVVM. Does ICollectionView can make it?

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• What about the Sql transaction log

  - by Michel

  Hi, i always thought that the sql transaction log keeps track of all the transactions done in the database so it could help recovering the database file in case of a unexpected power down or something like that So then, in normal usage, when the data is committed and written to disk, it is cleared because all the data is nice and safe in the mdf file. Seeing the ldf file grow and reading some i understand that that is not the case, and it will keep growing, until: you shrink the log. Only at that point all the commited transactions are cleared and the log file is shrinked. I found some sp's who should do this, but also found the theory that you first have to backup the database? That last step doesn't make sense to me, so can anyone tell me of that is correct and if so, why that is?

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• Dynamic Dispatch without Virtual Functions

  - by Kristopher Johnson

  I've got some legacy code that, instead of virtual functions, uses a kind field to do dynamic dispatch. It looks something like this: // Base struct shared by all subtypes // Plain-old data; can't use virtual functions struct POD { int kind; int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); }; enum Kind { Kind_Derived1, Kind_Derived2, Kind_Derived3 }; struct Derived1: POD { Derived1(): kind(Kind_Derived1) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived2: POD { Derived2(): kind(Kind_Derived2) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; struct Derived3: POD { Derived3(): kind(Kind_Derived3) {} int GetFoo(); int GetBar(); int GetBaz(); int GetXyzzy(); // plus other type-specific data and function members }; and then the POD class's function members are implemented like this: int POD::GetFoo() { // Call kind-specific function switch (kind) { case Kind_Derived1: { Derived1 *pDerived1 = static_cast<Derived1*>(this); return pDerived1->GetFoo(); } case Kind_Derived2: { Derived2 *pDerived2 = static_cast<Derived2*>(this); return pDerived2->GetFoo(); } case Kind_Derived3: { Derived3 *pDerived3 = static_cast<Derived3*>(this); return pDerived3->GetFoo(); } default: throw UnknownKindException(kind, "GetFoo"); } } POD::GetBar(), POD::GetBaz(), POD::GetXyzzy(), and other members are implemented similarly. This example is simplified. The actual code has about a dozen different subtypes of POD, and a couple dozen methods. New subtypes of POD and new methods are added pretty frequently, and so every time we do that, we have to update all these switch statements. The typical way to handle this would be to declare the function members virtual in the POD class, but we can't do that because the objects reside in shared memory. There is a lot of code that depends on these structs being plain-old-data, so even if I could figure out some way to have virtual functions in shared-memory objects, I wouldn't want to do that. So, I'm looking for suggestions as to the best way to clean this up so that all the knowledge of how to call the subtype methods is centralized in one place, rather than scattered among a couple dozen switch statements in a couple dozen functions. What occurs to me is that I can create some sort of adapter class that wraps a POD and uses templates to minimize the redundancy. But before I start down that path, I'd like to know how others have dealt with this.

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• n*n blocks and polygons

  - by OSaad

  Hi, this is actually meant to be for a function called roipoly in matlab but it can be considered a general case problem. Roipoly is a function which lets u select a polygon over an image, and returns a binary mask where u can use it to get indices of the desired polygon. (It is just a normal polygon after all). My application (K-Nearest Neighbor) requires that i make n*n blocks out of the data i have (the polygon), i.e. If i have a polygon (a road or a piece of land), i want a n*n square moving over it while avoiding intersection with edges and putting those n*n pixels into some variable. This problem would be a lot easier if i had all my shapes in the form of rectangles, but that unfortunately isn't the case. I might have something going diagonal, circular or just irregular.

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• Dynamic CCK fields population

  - by boogie

  Hi, How can I create two CCK fields where the latter has values based on the first selection? In my case I have a few programs which can be selected and then projects that are related to programs. I need to have two separate fields for them. Example: Programs: Program1 Program2 Projects: Project1 (related to Program1) Project2 (related to Program2) Project3 (related to Program2) If program "Program1" is selected, then the user should only be able to select "Project1" and in case of "Program2" is selected, the options should be "Project2" or "Project3". I'm using Drupal 6.20 and I've already tried using Conditional Fields and Computed Fields modules, but they don't really solve my problem. Any help is much appreciated!

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• How do you determine using stat() whether a file is a symbolic link?

  - by hora

  I basically have to write a clone of the UNIX ls command for a class, and I've got almost everything working. One thing I can't seem to figure out how to do is check whether a file is a symbolic link or not. From the man page for stat(), I see that there is a mode_t value defined, S_IFLNK. This is how I'm trying to check whether a file is a sym-link, with no luck (note, stbuf is the buffer that stat() returned the inode data into): switch(stbuf.st_mode & S_IFMT){ case S_IFLNK: printf("this is a link\n"); break; case S_IFREG: printf("this is not a link\n"); break; } My code ALWAYS prints this is not a link even if it is, and I know for a fact that the said file is a symbolic link since the actual ls command says so, plus I created the sym-link... Can anyone spot what I may be doing wrong? Thanks for the help!

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• Cocoa - Localized string from NSDate, NSCalendarDate...

  - by SirRatty

  I'm using NSDate to get a string such as "18 Jun 09", with code: NSDate *theDate = [NSDate date]; NSString *dateString = [theDate descriptionWithCalendarFormat:@"%d %b %y" timeZone:nil locale: nil]; This works, but only results in an English output. I need the output to be localized in the user's default language. Does Cocoa (Mac OS X 10.4, 10.5 in this case) provide a facility for this localization or do I have to manually localize for each case of day and & month names my self? (I have provided a locale, but although that does provide a locale-specific ordering of the date, it does not appear to do any localization of day-month names.)

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• Recommendations with hierarchical data on non-relational databases?

  - by Luki

  I'm developing an web application that uses a non-relational database as a backend (django-nonrel + AppEngine). I need to store some hierarchical data (projects/subproject_1/subproject_N/tasks), and I'm wondering which pattern should I use. For now I thought of: Adjacency List (store the item's parent id) Nested sets (store left and right values for the item) In my case, the depth of nesting for a normal user will not exceed 4-5 levels. Also, on the UI, I would like to have a pagination for the items on the first level, to avoid to load too many items at the first page load. From what I understand so far, nested sets are great when the hierarchy is used more for displaying. Adjacency lists are great when editing on the tree is done often. In my case I guess I need the displaying more than the editing (when using nested sets, even if the display would work great, the above pagination could complicate things on editing). Do you have any thoughts and advice, based on your experience with the non-relational databases?

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• PHP: How to Pass child class __construct() arguments to parent::__construct() ?

  - by none

  I have a class in PHP like so: class ParentClass { function __construct($arg) { // Initialize a/some variable(s) based on $arg } } It has a child class, as such: class ChildClass extends ParentClass { function __construct($arg) { // Let the parent handle construction. parent::__construct($arg); } } What if, for some reason, the ParentClass needs to change to take more than one optional argument, which I would like my Child class to provide "just in case"? Unless I re-code the ChildClass, it will only ever take the one argument to the constructor, and will only ever pass that one argument. Is this so rare or such a bad practice that the usual case is that a ChildClass wouldn't need to be inheriting from a ParentClass that takes different arguments? Essentially, I've seen in Python where you can pass a potentially unknown number of arguments to a function via somefunction(*args) where 'args' is an array/iterable of some kind. Does something like this exist in PHP? Or should I refactor these classes before proceeding?

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• What do you read?

  - by sixtyfootersdude

  I have almost finished reading all the articles on Joel on software. I am a new developer and hoping to get something interesting to read. Here is what is currently on my list: Java Concurrency in Practice by Brian Goetz sed & awk by Dougherty & Robbins (O'Reilly) The Pragmatic Programmer by Andrew Hunt and David Thomas Head First Design Patterns Can anyone suggest anything else? Would especially like something similar to Joel. Something that is a bit edgy but informative. Pragmatic programmer has some key concepts but is a bit dry.

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• Eager loading in EF1.0

  - by Dave Swersky

  I have a many-to-many relationship: Application - Applications_Servers - Server This is set up in my Entity Data Model and all is well. My problem is that I'd like to eager-load the whole graph of Applications so that I have an IEnumerable<Applications>, each Application member populated with the Servers collection associated by the many-to-many relationship. Normally this wouldn't be a problem, but according to my research there must be a navigation property between Application and Server. This is not the case for me because my Applications_Servers join table has more in it than just the two keys. Therefore, there is no navigation property directly between Application and Server, and this doesn't work: var apps = (from a in context.Application.Include("Server") select a).ToList(); I get an error saying there is no navigation property on Application called "Server", and that's correct, there is none. How do I write the query to eager-load my Applications with their Servers in this case?

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• Saving an IP adddress to DB

  - by Mark

  I want to save a user's IP address to my database just in case any legal issues come up and we need to track down who performed what action. Since I highly doubt I will ever actually need to use this data (well, maybe for counting unique hits or something) do you think I can just dump the REMOTE_ADDR into a field? If so, what should the length of that field be? 39 chars should fit an IPv6 address, no? I don't know if I'll ever get any of those, but just in case...

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• Is Jquery $(this) broken by jqgrid gridunload method?

  - by chohi

  I expect the following code to unload a javascipt jqgrid, then load another grid with different options, including different columns //onload (function($) $.fn.myGridFn = function(options){ $(this).jqGrid('GridUnload'); $(this).jqGrid(options.gridoptions); //.... $('#select').change(function(){ switch($(this).val()) { case 'grid1': $('#grid').myGridFn({gridoptions:{/*grid1 options*/}}); break; case 'grid2': $('#grid').myGridFn({gridoptions:{/*grid2 options*/}}); break; } }); })(jQuery); //... <table id="grid"></table> What I get is the grid unloading, then I have to change the selection in the select element and back again to load the new grid. Updated: If I replace the $(this) in the plugin with the actual element selector $('#grid') - it works just fine, I cant do this in my real app because the plugin is used by several other table elements and grids

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• Java Switch Incompatible Types Boolean Int

  - by ikurtz

  i have the following class: public class NewGameContract { public boolean HomeNewGame = false; public boolean AwayNewGame = false; public boolean GameContract(){ if (HomeNewGame && AwayNewGame){ return true; } else { return false; } } } when i try to use it like so: if (networkConnection){ connect4GameModel.newGameContract.HomeNewGame = true; boolean status = connect4GameModel.newGameContract.GameContract(); switch (status){ case true: break; case false: break; } return; } i am getting the error: incompatible types found: boolean required: int on the following switch (status) code. what am i doing wrong please?

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• os.path.getmtime() doesn't return fraction of a second

  - by haridsv

  I compile python 2.6.4 for centos 5.3 and find this issue that os.path.getmtime() or os.stat().m_time doesn't have the fraction part. As per docs, if os.stat_float_times() True, then it should return float value. In my case, I do see it as float, but no fraction part (it is 0). In [3]: os.path.getmtime('/tmp') Out[3]: 1268339116.0 In [4]: os.stat('/tmp') Out[4]: posix.stat_result(st_mode=17407, st_ino=508897L, st_dev=29952L, st_nlink=7, st_uid=0, st_gid=0, st_size=4096L, st_atime=1268101696, st_mtime=1268339116, st_ctime=1268339116) In [5]: os.stat_float_times() True In [6]: os.stat('/tmp').st_mtime Out[6]: 1268339116.0 It is also strange that the stat() output seems like an int. On windows, I do see a fraction part with the same python version. I am running centos on top of colinux, could that be playing a role, or is it some python build issue? I couldn't find any hits for generic colinux issue. May be it is how colinux configures the filesystem? What would I need to check in that case?

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• Approximate photo of a simple drawing using lines

  - by user3704596

  As an input I have a photo of a simple symbol, e.g.: https://www.dropbox.com/s/nrmsvfd0le0bkke/symbol.jpg I would like to detect the straight lines in it, like points of start and ends of the lines. In this case, assuming the top left of the symbol is (0,0), the lines would be defined like this: start end (coordinates of beginning and end of a line) 1. (0,0); (0,10) (vertical line) 2. (0,10); (15, 15) 3. (15,15); (0, 20) 4. (0,20); (0,30) How can I do it (pereferably using OpenCV)? I though about Hough lines, but they seem to be good for perfect thin straight lines, which is not the case in a drawing. I'll probably work on binarized image, too.

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• Java 7 API design best practice - return Array or return Collection

  - by Shengjie

  I know this question has be asked before generic comes out. Array does win out a bit given Array enforces the return type, it's more type-safe. But now, with latest JDK 7, every time when I design this type of APIs: public String[] getElements(String type) vs public List<String> getElements(String type) I am always struggling to think of some good reasons to return A Collection over An Array or another way around. What's the best practice when it comes to the case of choosing String[] or List as the API's return type? Or it's courses for horses. I don't have a special case in my mind, I am more looking for a generic pros/cons comparison.

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• Error handling and polymorphism

  - by Neeraj

  I have an application with some bunch of code like this: errCode = callMainSystem(); switch (errCode){ case FailErr: error("Err corresponding to val1\n"); case IgnoreErr: error("Err corresponding to val2\n"); ... ... default: error("Unknown error\n"); } The values are enum constants. Will it make some sense to have something like: // Error* callMainSystem() ... Some code return FaileErr(); // or some other error // handling code Error* err = callMainSystem(); err->toString(); The Error class may be made singleton as it only has to print error messages. What are the pros and cons of above methods,size is an important criteria as the application needs to be supported on embedded devices as well. P.S: I don't want to use exception handling because of portability issues and associated overheads.

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• How do I read a text file in Objective-c?

  - by danielDhobbs

  Can someone provide a simplest-case example of reading a text file.

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