Tutorial by Examples: r

Set operations

Operation : Average Case (assumes parameters generated randomly) : Worst case x in s : O(1) Difference s - t : O(len(s)) Intersection s&t : O(min(len(s), len(t))) : O(len(s) * len(t) Multiple intersection s1&s2&s3&...&sn : : (n-1) * O(l) where l is max(len(s1),...,len(sn)) s...

Python Language • Python speed of program

One or two parameters in callback—error handling in d3.request()

When using d3.request() or one of the convenience constructors (d3.json, d3.csv, d3.tsv, d3.html and d3.xml) there are many sources for error. There may be problems with the issued request or its response due to network errors, or the parsing might fail if the content is not well-formed. Within the...

d3.js • Using D3 with JSON and CSV

Splitting Strings using CROSS APPLY (Oracle 12c)

Sample Data: CREATE TABLE table_name ( id, list ) AS SELECT 1, 'a,b,c,d' FROM DUAL UNION ALL -- Multiple items in the list SELECT 2, 'e' FROM DUAL UNION ALL -- Single item in the list SELECT 3, NULL FROM DUAL UNION ALL -- NULL list SELECT 4, 'f,,g' FROM DUAL; -- NULL item...

Oracle Database • Splitting Delimited Strings

Encryption and Decryption using Cryptography (AES)

Decryption Code public static string Decrypt(string cipherText) { if (cipherText == null) return null; byte[] cipherBytes = Convert.FromBase64String(cipherText); using (Aes encryptor = Aes.Create()) { Rfc2898DeriveBytes pdb = ...

.NET Framework • Encryption / Cryptography

Getting details of Linux kernel.

We can use command uname with various options to get complete details of running kernel. uname -a Linux df1-ws-5084 4.4.0-64-generic #85-Ubuntu SMP Mon Feb 20 11:50:30 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux As per man page here few more options Usage: uname [OPTION]... Print certain system inf...

GNU/Linux • Getting information on a running Linux kernel

Replacing fragments with ajax

If you want to replace parts of your website, ajax is an easy way to do it. The website.html where you want to replace the content based on the selected value: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:th="http://www.thymeleaf.org"> ...

thymeleaf • Getting started with thymeleaf

Access to Request in a Twig or PHP template.

In Twig template, Request object is available at {{ app.request }} When you want display request method in Twig, try this: <p>Request method: {{ app.request.method }}</p> In PHP template <p>Request method: <?php echo $app->getRequest()->getMethod() ?></p>...

symfony2 • Request

Grouping a few input fields

While designing a form, you might like to group a few input fields into a group to help organise the form layout. This can be done by using the tag . Here is an example for using it. For each fieldset, you can set a legend for the set using the tag LEGEND TEXT Example <form> <fieldset...

HTML • Forms

Basic jumbotron with two lines of text and a button

This is a jumbotron with a title, a content and a button. Code <div class="jumbotron"> <h1>Title text</h1> <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec tortor ipsum, convallis sit.</p> <p><a class="btn btn-default&...

twitter-bootstrap • Jumbotron

Observer using IObservable and IObserver (C#)

IObserver<T> and IObservable<T> interfaces can be used to implement observer pattern in .NET IObservable<T> interface represents the class that sends notifications IObserver<T> interface represents the class that receives them public class Stock { private string Sym...

Design patterns • Observer

Adding the "Theme page title" item to the nav bar

Code function add_the_theme_page(){ add_menu_page('Theme page title', 'Theme menu label', 'manage_options', 'theme-options', 'page_content', 'dashicons-book-alt'); } add_action('admin_menu', 'add_the_theme_page'); function page_content(){ echo '<div class="wrap"><h2&...

WordPress • add_menu_page()

Secure your WebApp with Login and Logout

This example is a very simple Spring Boot application. Maven Dependencies At first add the following dependencies to your project. Spring Initializr is recommended when you create a new project. <parent> <groupId>org.springframework.boot</groupId> <artifactId>spr...

thymeleaf • Spring Security and Thymeleaf

Adding the "Submenu Page" as a sub-page of "Tools" to the nav bar

Code add_action('admin_menu', 'register_my_custom_submenu_page'); function register_my_custom_submenu_page() { add_submenu_page( 'tools.php', 'Submenu Page', 'My Custom Submenu Page', 'manage_options', 'my-custom-submenu-page', 'my_cust...

WordPress • add_submenu_page()

Show Character Set

Code <p><?php echo esc_html( sprintf( __( 'Character set: %s', 'textdomain' ), get_option( 'blog_charset' ) ) ); ?></p> Output Character set: UTF-8

WordPress • get_option()

Reshape from wide to long format with gather()

library(tidyr) ## example data df <- read.table(text =" numbers firstName secondName 1 1 1.5862639 0.4087477 2 2 0.1499581 0.9963923 3 3 0.4117353 0.3740009 4 4 -0.4926862 0.4437916", header = T) df # numbers firstName secondName # 1 ...

R Language • Reshape using tidyr

Making a button in your UI that pauses callback execution

Sometimes we'd like to pause code execution to inspect the state of the application (see Debugging). When running code through the MATLAB editor, this can be done using the "Pause" button in the UI or by pressing Ctrl+c (on Windows). However, when a computation was initiated from a GUI (vi...

MATLAB Language • MATLAB User Interfaces

Creating a video with OpenCV (Java)

VideoWriter videoWriter; videoWriter = new VideoWriter(outputFile, VideoWriter.fourcc('x', '2','6','4'), fps, frameSize, isRGB); //We have stated that we will use x264 as codec with FourCC //For writing, we add the following method and it will write the image we give as parameter...

opencv • Creating a Video

pseudocode for a dumb file manager

/* * Component is an interface * which all elements (files, * folders, links ...) will implement */ class Component { public: virtual int getSize() const = 0; }; /* * File class represents a file * in file system. */ class File : public Component { public: virtual int...

Design patterns • Composite pattern

Using Blocks for Recurring Elements

One of the most useful things that came along with sections is blocks. Blocks are basically a blueprint for something that can be created an unlimited amount of times. One of the best examples is the slides of a slider. A block is a top level item in the schema, meaning it is alongside things like n...

Shopify • Implementing Sections

Open Close Principle violation

/* * This design have some major issues * For each new shape added the unit testing * of the GraphicEditor should be redone * When a new type of shape is added the time * for adding it will be high since the developer * who add it should understand the logic * of the Gr...

Design patterns • Open Close Principle