Search Results

Search found 9932 results on 398 pages for 'pseudo element'.

Page 182/398 | < Previous Page | 178 179 180 181 182 183 184 185 186 187 188 189  | Next Page >

  • Remove Empty Attributes from XML

    - by er4z0r
    Hi, I have a buggy xml that contains empty attributes and I have a parser that coughs on empty attributes. I have no control over the generation of the xml nor over the parser that coughs on empty attrs. So what I want to do is a pre-processing step that simply removes all empty attributes. I have managed to find the empty attribus, but now I don't know how to remove them: XPathFactory xpf = XPathFactory.newInstance(); XPath xpath = xpf.newXPath(); XPathExpression expr = xpath.compile("//@*"); Object result = expr.evaluate(d, XPathConstants.NODESET); if (result != null) { NodeList nodes = (NodeList) result; for(int node=0;node<nodes.getLength();node++) { Node n = nodes.item(node); if(isEmpty(n.getTextContent())) { this.log.warn("Found empty attribute declaration "+n.toString()); NamedNodeMap parentAttrs = n.getParentNode().getAttributes(); parentAttrs.removeNamedItem(n.getNodeName()); } } } This code gives me a NPE when accessing n.getParentNode().getAttributes(). But how can I remove the empty attribute from an element, when I cannot access the element?

    Read the article

  • Using StructureMap to create classes by a name?

    - by Bevan
    How can I use StructureMap to resolve to an appropriate implementation of an interface based on a name stored in an attribute? In my project, I have many different kinds of widgets, each descending from IWidget, and each decorated with an attribute specifying the kind of associated element. To illustrate: [Configuration("header")] public class HeaderWidget : IWidget { } [Configuration("linegraph")] public class LineGraphWidget : IWidget { } When processing my (XML) configuration file, I want to obtain an instance of the appropriate concrete class based on the name of the element I'm processing. public IWidget CreateWidget(XElement definition) { var kind = definition.Name.LocalName; var widget = // What goes here? widget.Configure(definition); return widget; } Each definition should result in a different widget being created - I don't need or want the instances to be shared. In the past I've written plenty of code to do this kind of thing manually, including writing a custom "roll-your-own" IoC container for one project. However, one of my goals with this project is to become proficient with StructureMap instead of reinventing the wheel. I think I've already managed to set up automatic scanning of assemblies so that StructureMap knows about all my IWidget implementations: public class WidgetRegistration : Registry { public WidgetRegistration() { Scan( scanner => { scanner.AssembliesFromApplicationBaseDirectory(); scanner.AddAllTypesOf<IWidget>(); }); } } However, this isn't registering the names of my widgets with StructureMap. What do I need to add to make my scenario work? (While I am trying to use StructureMap in this project, an answer showing me how to solve this problem with a different DI/IoC tool would still be valuable.)

    Read the article

  • How to access elements in a complex list?

    - by Martin
    Hi, it's me and the lists again. I have a nice list, which looks like this: tmp = NULL t = NULL tmp$resultitem$count = "1057230" tmp$resultitem$status = "Ok" tmp$resultitem$menu = "PubMed" tmp$resultitem$dbname = "pubmed" t$resultitem$count = "305215" t$resultitem$status = "Ok" t$resultitem$menu = "PMC" t$resultitem$dbname = "pmc" tmp = c(tmp, t) t = NULL t$resultitem$count = "1" t$resultitem$status = "Ok" t$resultitem$menu = "Journals" t$resultitem$dbname = "journals" tmp = c(tmp, t) Which produces: str(tmp) List of 3 $ resultitem:List of 4 ..$ count : chr "1057230" ..$ status: chr "Ok" ..$ menu : chr "PubMed" ..$ dbname: chr "pubmed" $ resultitem:List of 4 ..$ count : chr "305215" ..$ status: chr "Ok" ..$ menu : chr "PMC" ..$ dbname: chr "pmc" $ resultitem:List of 4 ..$ count : chr "1" ..$ status: chr "Ok" ..$ menu : chr "Journals" ..$ dbname: chr "journals" Now I want to search through the elements of each "resultitem". I want to know the "dbname" for every database, that has less then 10 "count" (example). In this case it is very easy, as this list only has 3 elements, but the real list is a little bit longer. This could be simply done with a for loop. But is there a way to do this with some other function of R (like rapply)? My problem with those apply functions is, that they only look at one element. If I do a grep to get all "dbname" elements, I can not get the count of each element. rapply(tmp, function(x) paste("Content: ", x))[grep("dbname", names(rapply(tmp, c)))] Does someone has a better idea than a for loop? Thanx, Martin

    Read the article

  • mediaelement.js play/pause on click controls don't work

    - by iKode
    I need to play and pause the video player if any part of the video is clicked, so I implemented something like: $("#promoPlayer").click(function() { $("#promoPlayer").click(function() { if(this.paused){ this.play(); } else { this.pause(); } }); ...but now the controls of the video won't pause/play. You can see it in action here(http://175.107.134.113:8080/). The video is the second slide on the main carousel at the top. I suspect I'm now getting 2 onclick events one from my code above and a second on the actual pause/play button. I don't understand how the actual video controls work, because when I inspect the element, I just see a tag. If I could differentiate the controls, then perhaps I might have figured out a solution by now. Anyone know how I should have done this, or is my solution ok. If my solutions ok, how do I intercept a click on the control, so that I only have one click event to pause / play? If you look on the media element home page, they have a big play button, complete with mouseOver, but I can't see how they have done that? Can someone else help?

    Read the article

  • array_splice() - Numerical Offsets of Associative Arrays

    - by Alix Axel
    I'm trying to do something but I can't find any solution, I'm also having some trouble putting it into works so here is a sample code, maybe it'll be enough to demonstrate what I'm aiming for: $input = array ( 'who' => 'me', 'what' => 'car', 'more' => 'car', 'when' => 'today', ); Now, I want to use array_splice() to remove (and return) one element from the array: $spliced = key(array_splice($input, 2, 1)); // I'm only interested in the key... The above will remove and return 1 element (third argument) from $input (first argument), at offset 2 (second argument), so $spliced will hold the value more. I'll be iterating over $input with a foreach loop, I know the key to be spliced but the problem is I don't know its numerical offset and since array_splice only accepts integers I don't know what to do. A very dull example: $result = array(); foreach ($input as $key => $value) { if ($key == 'more') { // Remove the index "more" from $input and add it to $result. $result[] = key(array_splice($input, 2 /* How do I know its 2? */, 1)); } } I first though of using array_search() but it's pointless since it'll return the associative index.... How do I determine the numerical offset of a associative index?

    Read the article

  • Assemble an image browser side with JavaScript or Flash?

    - by Kris Walker
    Would it be possible to assemble an image on the browser by 'concatenating' other downloaded images together? The use case is this. The page will display 36 different tiles (small images). The user should be able to arrange those tiles into a 6 x 6 grid and save the resulting grid to disk as an image. The best solution would be to do it all in the browser without Flash. The next best solution would be to allow the user to create the grid in the browser with simple JavaScript drag and drop functionality and then send the coordinates to the server for image processing. The last solution would be to do it all in the browser with Flash. Is it even possible for Flash to create an image and then allow the user to save it from the browser? I am familiar with the Pixastic JavaScript library ( http://www.pixastic.com/ ), but it relies on getting image data to and from a canvas element which is not very well supported. What if I send the tile images to the browser as base64 encoded strings? Could I use JavaScript to create the 6 x 6 grid image? And if so, is there some way of allowing the user to get it onto disk without relying on the canvas element?

    Read the article

  • Find min. "join" operations for sequence

    - by utyle
    Let's say, we have a list/an array of positive integers x1, x2, ... , xn. We can do a join operation on this sequence, that means that we can replace two elements that are next to each other with one element, which is sum of these elements. For example: - array/list: [1;2;3;4;5;6] we can join 2 and 3, and replace them with 5; we can join 5 and 6, and replace them with 11; we cannot join 2 and 4; we cannot join 1 and 3 etc. Main problem is to find minimum join operations for given sequence, after which this sequence will be sorted in increasing order. Note: empty and one-element sequences are sorted in increasing order. Basic examples: for [4; 6; 5; 3; 9] solution is 1 (we join 5 and 3) for [1; 3; 6; 5] solution is also 1 (we join 6 and 5) What I am looking for, is an algorithm that solve this problem. It could be in pseudocode, C, C++, PHP, OCaml or similar (I mean: I woluld understand solution, if You wrote solution in one of these languages). I would appreciate Your help.

    Read the article

  • How to make std::vector's operator[] compile doing bounds checking in DEBUG but not in RELEASE

    - by Edison Gustavo Muenz
    I'm using Visual Studio 2008. I'm aware that std::vector has bounds checking with the at() function and has undefined behaviour if you try to access something using the operator [] incorrectly (out of range). I'm curious if it's possible to compile my program with the bounds checking. This way the operator[] would use the at() function and throw a std::out_of_range whenever something is out of bounds. The release mode would be compiled without bounds checking for operator[], so the performance doesn't degrade. I came into thinking about this because I'm migrating an app that was written using Borland C++ to Visual Studio and in a small part of the code I have this (with i=0, j=1): v[i][j]; //v is a std::vector<std::vector<int> > The size of the vector 'v' is [0][1] (so element 0 of the vector has only one element). This is undefined behaviour, I know, but Borland is returning 0 here, VS is crashing. I like the crash better than returning 0, so if I can get more 'crashes' by the std::out_of_range exception being thrown, the migration would be completed faster (so it would expose more bugs that Borland was hiding).

    Read the article

  • Javascript Function for related select elements onSubmit

    - by Livingston
    I am trying to create (4) Select elements within a form element. Each select element has a different number of options. So if a user click one option on Select #1 and then click another option on Select #2, after hitting submit they will be taken to www.blah.com/option1/option2 page which will display the filtered results. Or they can chose an option from all 4 select menus and be taken to option1/option2/option3/option4 page. The categories are all related .Select #1 is a category, Select #2 is a subcategory of 1, Select #3 is a subcategory of #2 and Select #4 is a subcategory of #3. A great example would be on (LINK) http://www.safavieh.com/rugs (LINK) except only four Select elements. I would also like to add the "Reset" button next to "Submit." I know I need to construct a function in my header and use onSubmit attribute within the form but other than that I am unsure of what's involved so I'm hoping someone could point me in the right direction. It's important I learn most of this for myself. Thanks for your time Livingston

    Read the article

  • Array of templated structs

    - by Jakub Mertlik
    I have structs templated by int derived from a Base struct. struct Base { int i; double d; }; template< int N > struct Derv : base { static const int mN = N; }; I need to make an array of Derv< N where N can vary for each struct in that array. I know C/C++ does not allow arrays of objects of different types, but is there a way around this? I was thinking of separating the type information somehow (hints like pointers to Base struct or usage of union spring to my mind, but with all of these I don't know how to store the type information of each array element for usage DURING COMPILE TIME). As you can see, the memory pattern of each Derv< N is the same. I need to access the type of each array element for template specialization later in my code. The general aim of this all is to have a compile-time dispatch mechanism without the need to do a runtime "type switch" somewhere in the code. Thank you.

    Read the article

  • Swapping content in a seperate div on hover

    - by Fuego DeBassi
    I feel like this should work: $(".module .one").hover(function() { $("#viewport #one").addClass('red'); }); Basically I am hiding all the .children of "#viewport on load, then when a seperate element is hovered, in this case .module .one I want to change something on the corresponding viewport ID #viewport #one. Basic idea is a variable content window, where when a thumbnail or whatever I put in the modules swaps the content shown in the viewport. Something I am doing wrong? Here is my full code: <script type="text/javascript"> $(document).ready(function() { $(".module .caption").hide(); $("#viewport").children().hide(); $(".module").hover(function() { $(this).find(".caption").slideDown().end().siblings('.module').addClass('under'); },function() { $(this).find(".caption").slideUp().end().siblings('.module').removeClass('under'); }); $(".module .one").hover(function() { $("#viewport #one").addClass('red'); }); }); </script> The bigger hover function in the middle is for some fancy rollover effects that the modules will perform themselves, but for these purposes I just want to figure out why I can't add a Class to a separate element when another is hovered. Would love some help/advice!

    Read the article

  • JQuery Dragging Outside Parent

    - by Andy
    I'm using JQuery's draggable(); to make li elements draggable. The only problem is when the element is dragged outside its parent, it doesn't show up. That is, it doesn't leave the confines of its parent div. An example is here: http://imgur.com/N2N1L.png - it's as if the z-index for everything else has greater priority (and the element slides under everything). Here's the code: $('.photoList li').draggable({ distance: 20, snap: theVoteBar, revert: true, containment: 'document' }); And the li elements are placed in DIVs like this: <div class="coda-slider preload" id="coda-slider-1"> <div class="panel"> <div class="panel-wrapper"> <h2 class="title" style="display:none;">Page 1</h2> <ul class="photoList"> <li> <img class="ui-widget-content" src="photos/1.jpg" style="width:100px;height:100px;" /> </li> </ul> </div> </div> I'm positive the problem is it won't leave its parent container, but I'm not sure what to do to get it out. Any direction or help would be appreciated GREATLY!

    Read the article

  • JQuery set img src depending on where you click

    - by Anna
    Hello ! I used javascript for loading a picture on my website depending on which "small" photos in ul you clicked... I had something like that : <script type="text/javascript"> function viewImage(src, legende) { document.getElementById("imageBig").src = "images/photos/"+src; document.getElementById("legend").innerHTML = legende; } </script> and in html simply : things like that : <li><a href="#centre" onclick="javascript:viewImage('flute.jpg','La Reine de la Nuit au Comedia')"><img src="images/photos/carre-09.jpg" alt="" /></a> <a href="#centre" onclick="javascript:viewImage('perichole.jpg','Manuelita - <em>La P&eacute;richole</em> &agrave; l&#8217;Op&eacute;ra Comique')"><img src="images/photos/carre-03.jpg" alt="" /></a></li> <li><a href="#centre" onclick="javascript:viewImage('12.png','R&eacute;cital &agrave; Carnac, septembre 2008')"><img src="images/photos/carre-12.jpg" alt="Marion Baglan Carnac R&eacute;" /></a> <a href="#centre" onclick="javascript:viewImage('01.jpg','')"><img src="images/photos/carre-01.jpg" alt="" /></a></li> so you see, I could, depending on which small photos in the unordered list you clicked, load some particular photos, by passing the src string in argument... but I decided to use Jquery to get some fade-in effect. But I can't find a way to pass an argument that would tell my JQuery function which photo to load depending on where I clicked... stuck here : $(document).ready(function(){ $('#ulPhotos').click(function() { var newSrc= $('#imageBig').attr("src", "images/photos/11.jpg"); }); }); I don't want the 11.jpg to be hardcoded, I need to pass it through argument when I click on a special li element in my ul element of id #ulPhotos... I hope I'm clear enough sorry !

    Read the article

  • POST XML to server, receive PDF

    - by Shaggy Frog
    Similar to this question, we are developing a Web app where the client clicks a button to receive a PDF from the server. Right now we're using the .ajax() method with jQuery to POST the data the backend needs to generate the PDF (we're sending XML) when the button is pressed, and then the backend is generating the PDF entirely in-memory and sending it back as application/pdf in the HTTP response. One answer to that question requires the server-side save the PDF to disk so it can give back a URL for the client to GET. But I don't want the backend caching content at all. The other answer suggests the use of a jQuery plugin, but when you look at its code, it's actually generating a form element and then submitting the form. That method will not work for us since we are sending XML data in the body of the HTTP request. Is there a way to have the browser open up the PDF without caching the PDF server-side, and without requiring us to throw out our send-data-to-the-server-using-XML solution? (I'd like the browser to behave like it does when a form element is submitted -- a POST is made and then the browser looks at the Content-type header to determine what to do next, like load the PDF in the browser window, a la Safari)

    Read the article

  • Conditional operator in Mako using Pylons

    - by Antoine Leclair
    In PHP, I often use the conditional operator to add an attribute to an html element if it applies to the element in question. For example: <select name="blah"> <option value="1"<?= $blah == 1 ? ' selected="selected"' : '' ?>> One </option> <option value="2"<?= $blah == 2 ? ' selected="selected"' : '' ?>> Two </option> </select> I'm starting a project with Pylons using Mako for the templating. How can I achieve something similar? Right now, I see two possibilities that are not ideal. Solution 1: <select name="blah"> % if blah == 1: <option value="1" selected="selected">One</option> % else: <option value="1">One</option> % endif % if blah == 2: <option value="2" selected="selected">Two</option> % else: <option value="2">Two</option> % endif </select> Solution 2: <select name="blah"> <option value="1" % if blah == 1: selected="selected" % endif >One</option> <option value="2" % if blah == 2: selected="selected" % endif >Two</option> </select> In this particular case, the value is equal to the variable tested (value="1" = blah == 1), but I use the same pattern in other situations, like <?= isset($variable) ? ' value="$variable" : '' ?>. I am looking for a clean way to achieve this using Mako.

    Read the article

  • Natural problems to solve using closures

    - by m.u.sheikh
    I have read quite a few articles on closures, and, embarassingly enough, I still don't understand this concept! Articles explain how to create a closure with a few examples, but I don't see any point in paying much attention to them, as they largely look contrived examples. I am not saying all of them are contrived, just that the ones I found looked contrived, and I dint see how even after understanding them, I will be able to use them. So in order to understand closures, I am looking at a few real problems, that can be solved very naturally using closures. For instance, a natural way to explain recursion to a person could be to explain the computation of n!. It is very natural to understand a problem like computing the factorial of a number using recursion. Similarly, it is almost a no-brainer to find an element in an unsorted array by reading each element, and comparing with the number in question. Also, at a different level, doing Object-oriented programming also makes sense. So I am trying to find a number of problems that could be solved with or without closures, but using closures makes thinking about them and solving them easier. Also, there are two types to closures, where each call to a closure can create a copy of the environment variables, or reference the same variables. So what sort of problems can be solved more naturally in which of the closure implementations?

    Read the article

  • Problem using js jquery helper

    - by Josh R
    hi, I am using cakephp 1.3.6 and am trying to use inbuilt js helper. I have added var $helpers = array('Js' => array('Jquery')); in my controller. In my layout, I have included the jquery files and have also included echo $this->Js->writeBuffer(); before the </body> tag. I checked if the jquery libraries correctly but trying to create a simple accordian from the jqueryui.com, it works fine. But when I try <?php $this->Js->get('#element'); $this->Js->drag(array( 'container' => '#content', 'start' => 'onStart', 'drag' => 'onDrag', 'stop' => 'onStop', 'snapGrid' => array(10, 10), 'wrapCallbacks' => false )); ?> <div="element">something</div> It does not work. I appreciate any help. Thanks.

    Read the article

  • Ternary operator

    - by Antoine Leclair
    In PHP, I often use the ternary operator to add an attribute to an html element if it applies to the element in question. For example: <select name="blah"> <option value="1"<?= $blah == 1 ? ' selected="selected"' : '' ?>> One </option> <option value="2"<?= $blah == 2 ? ' selected="selected"' : '' ?>> Two </option> </select> I'm starting a project with Pylons using Mako for the templating. How can I achieve something similar? Right now, I see two possibilities that are not ideal. Solution 1: <select name="blah"> % if blah == 1: <option value="1" selected="selected">One</option> % else: <option value="1">One</option> % endif % if blah == 2: <option value="2" selected="selected">Two</option> % else: <option value="2">Two</option> % endif </select> Solution 2: <select name="blah"> <option value="1" % if blah == 1: selected="selected" % endif >One</option> <option value="2" % if blah == 2: selected="selected" % endif >Two</option> </select> In this particular case, the value is equal to the variable tested (value="1" = blah == 1), but I use the same pattern in other situations, like <?= isset($variable) ? ' value="$variable" : '' ?>. I am looking for a clean way to achieve this using Mako.

    Read the article

  • asp.net jquery how to use Plugin/Validation with web content

    - by Eyla
    I have a asp.net web content from that have a asp.net textbox and I want to use Plugin/Validation but it is not working with me here is my code: <%@ Page Title="" Language="C#" MasterPageFile="~/Master.Master" AutoEventWireup="true" CodeBehind="WebForm1.aspx.cs" Inherits="IMAM_APPLICATION.WebForm1" %> <%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %> <asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server"> <script src="js/jquery-1.4.1.js" type="text/javascript"></script> <script src="js/jquery.validate.js" type="text/javascript"></script> <script type="text/javascript"> $(document).ready(function() { $.validator.addMethod("#<%=TextBox1.ClientID %>", function(value, element) { return this.optional(element) || /^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,16}$/i.test(value); }, "Passwords are 8-16 characters with uppercase letters, lowercase letters and at least one number."); }); </script> </asp:Content> <asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> </asp:Content> <asp:Content ID="Content3" ContentPlaceHolderID="ContentPlaceHolder2" runat="server"> <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox> </asp:Content>

    Read the article

  • R: manipulating data.frames containing strings and booleans.

    - by Mike Dewar
    Hello. I have a data.frame in R; it's called p. Each element in the data.frame is either True or False. My variable p has, say, m rows and n columns. For every row there is strictly only one TRUE element. It also has column names, which are strings. What I would like to do is the following: For every row in p I see a TRUE I would like to replace with the name of the corresponding column I would then like to collapse the data.frame, which now contains FALSEs and column names, to a single vector, which will have m elements. I would like to do this in an R-thonic manner, so as to continue my enlightenment in R and contribute to a world without for-loops. I can do step 1 using the following for loop: for (i in seq(length(colnames(p)))) { p[p[,i]==TRUE,i]=colnames(p)[i] } but theres's no beauty here and I have totally subscribed to this for-loops-in-R-are-probably-wrong mentality. Maybe wrong is too strong but they're certainly not great. I don't really know how to do step 2. I kind of hoped that the sum of a string and FALSE would return the string but it doesn't. I kind of hoped I could use an OR operator of some kind but can't quite figure that out (Python responds to False or 'bob' with 'bob'). Hence, yet again, I appeal to you beautiful Rstats people for help!

    Read the article

  • How best to associate code with events in jQuery?

    - by Ned Batchelder
    Suppose I have a <select> element on my HTML page, and I want to run some Javascript when the selection is changed. I'm using jQuery. I have two ways to associate the code with the element. Method 1: jQuery .change() <select id='the_select'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> $('#the_select').change(function() { alert('Changed!'); }); </script> Method 2: onChange attribute <select id='the_select' onchange='selectChanged();'> <option value='opt1'>One</option> <option value='opt2'>Two</option> </select> <script> function selectChanged() { alert('Changed!'); } </script> I understand the different modularity here: for example, method 1 keeps code references out of the HTML, but method 2 doesn't need to mention HTML ids in the code. What I don't understand is: are there operational differences between these two that would make me prefer one over the other? For example, are there edge-case browsers where one of these works and the other doesn't? Is the integration with jQuery better for either? Does the late-binding of the code to the event make a difference in the behavior of the page? Which do you pick and why?

    Read the article

  • Best method to select an object from another unknown jQuery object

    - by Yosi
    Lets say I have a jQuery object/collection stored in a variable named obj, which should contain a DOM element with an id named target. I don't know in advance if target will be a child in obj, i.e.: obj = $('<div id="parent"><div id="target"></div></div>'); or if obj equals target, i.e.: obj = $('<div id="target"></div>'); or if target is a top-level element inside obj, i.e.: obj = $('<div id="target"/><span id="other"/>'); I need a way to select target from obj, but I don't know in advance when to use .find and when to use .filter. What would be the fastest and/or most concise method of extracting target from obj? What I've come up with is: var $target = obj.find("#target").add(obj.filter("#target")); UPDATE I'm adding solutions to a JSPERF test page to see which one is the best. Currently my solution is still the fastest. Here is the link, please run the tests so that we'll have more data: http://jsperf.com/jquery-selecting-objects

    Read the article

  • Behavior of <- NULL on lists versus data.frames for removing data

    - by Ananda Mahto
    Many R users eventually figure out lots of ways to remove elements from their data. One way is to use NULL, particularly when you want to do something like drop a column from a data.frame or drop an element from a list. Eventually, a user comes across a situation where they want to drop several columns from a data.frame at once, and they hit upon <- list(NULL) as the solution (since using <- NULL will result in an error). A data.frame is a special type of list, so it wouldn't be too tough to imagine that the approaches for removing items from a list should be the same as removing columns from a data.frame. However, they produce different results, as can be seen in the example below. ## Make some small data--two data.frames and two lists cars1 <- cars2 <- head(mtcars)[1:4] cars3 <- cars4 <- as.list(cars2) ## Demonstration that the `list(NULL)` approach works cars1[c("mpg", "cyl")] <- list(NULL) cars1 # disp hp # Mazda RX4 160 110 # Mazda RX4 Wag 160 110 # Datsun 710 108 93 # Hornet 4 Drive 258 110 # Hornet Sportabout 360 175 # Valiant 225 105 ## Demonstration that simply using `NULL` does not work cars2[c("mpg", "cyl")] <- NULL # Error in `[<-.data.frame`(`*tmp*`, c("mpg", "cyl"), value = NULL) : # replacement has 0 items, need 12 Switch to applying the same concept to a list, and compare the difference in behavior. ## Does not fully drop the items, but sets them to `NULL` cars3[c("mpg", "cyl")] <- list(NULL) # $mpg # NULL # # $cyl # NULL # # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 ## *Does* drop the `list` items while this would ## have produced an error with a `data.frame` cars4[c("mpg", "cyl")] <- NULL # $disp # [1] 160 160 108 258 360 225 # # $hp # [1] 110 110 93 110 175 105 The main questions I have are, if a data.frame is a list, why does it behave so differently in this scenario? Is there a foolproof way of knowing when an element will be dropped, when it will produce an error, and when it will simply be given a NULL value? Or do we depend on trial-and-error for this?

    Read the article

  • Pairs from single list

    - by Apalala
    Often enough, I've found the need to process a list by pairs. I was wondering which would be the pythonic and efficient way to do it, and found this on Google: pairs = zip(t[::2], t[1::2]) I thought that was pythonic enough, but after a recent discussion involving idioms versus efficiency, I decided to do some tests: import time from itertools import islice, izip def pairs_1(t): return zip(t[::2], t[1::2]) def pairs_2(t): return izip(t[::2], t[1::2]) def pairs_3(t): return izip(islice(t,None,None,2), islice(t,1,None,2)) A = range(10000) B = xrange(len(A)) def pairs_4(t): # ignore value of t! t = B return izip(islice(t,None,None,2), islice(t,1,None,2)) for f in pairs_1, pairs_2, pairs_3, pairs_4: # time the pairing s = time.time() for i in range(1000): p = f(A) t1 = time.time() - s # time using the pairs s = time.time() for i in range(1000): p = f(A) for a, b in p: pass t2 = time.time() - s print t1, t2, t2-t1 These were the results on my computer: 1.48668909073 2.63187503815 1.14518594742 0.105381965637 1.35109519958 1.24571323395 0.00257992744446 1.46182489395 1.45924496651 0.00251388549805 1.70076990128 1.69825601578 If I'm interpreting them correctly, that should mean that the implementation of lists, list indexing, and list slicing in Python is very efficient. It's a result both comforting and unexpected. Is there another, "better" way of traversing a list in pairs? Note that if the list has an odd number of elements then the last one will not be in any of the pairs. Which would be the right way to ensure that all elements are included? I added these two suggestions from the answers to the tests: def pairwise(t): it = iter(t) return izip(it, it) def chunkwise(t, size=2): it = iter(t) return izip(*[it]*size) These are the results: 0.00159502029419 1.25745987892 1.25586485863 0.00222492218018 1.23795199394 1.23572707176 Results so far Most pythonic and very efficient: pairs = izip(t[::2], t[1::2]) Most efficient and very pythonic: pairs = izip(*[iter(t)]*2) It took me a moment to grok that the first answer uses two iterators while the second uses a single one. To deal with sequences with an odd number of elements, the suggestion has been to augment the original sequence adding one element (None) that gets paired with the previous last element, something that can be achieved with itertools.izip_longest().

    Read the article

  • How to merge objects in php ?

    - by The Devil
    Hey everybody, I'm currently re-writing a class which handles xml files. Depending on the xml file and it's structure I sometimes need to merge objects. Lets say once I have this: <page name="a title"/> And another time I have this: <page name="a title"> <permission>administrator</permission> </page> Before, I needed only the attributes from the "page" element. That's why a lot of my code expects an object containing only the attributes ($loadedXml-attributes()). Now there are xml files in which the <permission> element is required. I did manage to merge the objects (though not as I wanted) but I can't get to access one of them (most probably it's something I'm missing). To merge my objects I used this code: (object) array_merge( (array) $loadedXml->attributes(), (array) $loadedXml->children() ); This is what I get from print_r(): stdClass Object ( [@attributes] => Array ( [name] => a title ) [permission] => Array ( [0] => administrator ) ) So now my question is how to access the @attributes method ? Thanks in advance, The Devil

    Read the article

< Previous Page | 178 179 180 181 182 183 184 185 186 187 188 189  | Next Page >