Tutorial by Examples: r

The most common way to install the RSpec gem is using Bundler. Add this line to your application's Gemfile: gem 'rspec' And then execute bundle to install the dependencies: $ bundle Alternatively, you can install the gem manually: $ gem install rspec After installing the gem, run the fol...

When an extension method returns a value that has the same type as its this argument, it can be used to "chain" one or more method calls with a compatible signature. This can be useful for sealed and/or primitive types, and allows the creation of so-called "fluent" APIs if the me...

import flash.net.URLRequest; import flash.media.Sound; import flash.events.Event; var req:URLRequest = new URLRequest("click.mp3"); var snd:Sound = new Sound(req); snd.addEventListener(Event.COMPLETE, function(e: Event) { snd.play(); }

There are situations when you need to calculate something really large in your Flash application, while not interrupting the user's experience. For this, you need to devise your lengthy process as a multi-step process with saved state between iterations. For example, you need to perform a background...

Shiny is an R package developed by RStudio that allows the creation of web pages to interactively display the results of an analysis in R. There are two simple ways to create a Shiny app: in one .R file, or in two files: ui.R and server.R. A Shiny app is divided into two parts: ui: A user...

Prerequisites sudo apt-get install build-essential sudo apt-get install python [optional] sudo apt-get install git Get source and build cd ~ git clone https://github.com/nodejs/node.git OR For the latest LTS Node.js version 6.10.2 cd ~ wget https://nodejs.org/dist/v6.3.0/node-v6.10....

This is a short summary of the GitLab guide on Install a GitLab CE Omnibus package. Requirements In order to install the GitLab Community Edition on your server, you should read the requirements page. To make it brief, the recommended requirements are: OS: Ubuntu, Debian, CentOS, RHEL Ruby ver...

The Iterator.remove() method is an optional method that removes the element returned by the previous call to Iterator.next(). For example, the following code populates a list of strings and then removes all of the empty strings. List<String> names = new ArrayList<>(); names.add("...

The only way to catch exception in initializer list: struct A : public B { A() try : B(), foo(1), bar(2) { // constructor body } catch (...) { // exceptions from the initializer list and constructor are caught here // if no exception is thrown h...

void function_with_try_block() try { // try block body } catch (...) { // catch block body } Which is equivalent to void function_with_try_block() { try { // try block body } catch (...) { // catch block body } } Note t...

struct A { ~A() noexcept(false) try { // destructor body } catch (...) { // exceptions of destructor body are caught here // if no exception is thrown here // then the caught exception is re-thrown. } }; Note that, although this...

Transformations are done with respect to a point which is defined by the transform-origin property. The property takes 2 values : transform-origin: X Y; In the following example the first div (.tl) is rotate around the top left corner with transform-origin: 0 0; and the second (.tr)is transformed ...

With Maven you can create Vaadin project with vaadin-archetype-application archetype. You can also add that archetype in IDE to create maven project with IDE. mvn archetype:generate -DarchetypeGroupId=com.vaadin -DarchetypeArtifactId=vaadin-archetype-application -DarchetypeVersion=7....

Function application syntax in Elm does not use parenthesis or commas, and is instead whitespace-sensitive. To define a function, specify its name multiplyByTwo and arguments x, any operations after equal sign = is what returned from a function. multiplyByTwo x = x * 2 To call a function, ...

Elm has a special syntax for lambda expressions or anonymous functions: \arguments -> returnedValue For example, as seen in List.filter: > List.filter (\num -> num > 1) [1,2,3] [2,3] : List number More to the depth, a backward slash, \, is used to mark the beginning of lambda ex...

It is possible to define local variables inside a function to reduce code repetition give name to subexpressions reduce the amount of passed arguments. The construct for this is let ... in .... bigNumbers = let allNumbers = [1..100] isBig number = ...

It is very convenient to use extension methods with interfaces as implementation can be stored outside of class and all it takes to add some functionality to class is to decorate class with interface. public interface IInterface { string Do() } public static class ExtensionMethods{ pu...

File streams are buffered by default, as are many other types of streams. This means that writes to the stream may not cause the underlying file to change immediately. In oder to force all buffered writes to take place immediately, you can flush the stream. You can do this either directly by invokin...

List employees earning more than $50000 born this century. List their name, date of birth and salary, sorted alphabetically by name. SELECT employee_name, date_of_birth, salary FROM employees WHERE salary > 50000 AND date_of_birth >= DATE '2000-01-01' ORDER BY employee_name; Show...

In [1]: df1 = pd.DataFrame({'x': [1, 2, 3], 'y': ['a', 'b', 'c']}) In [2]: df2 = pd.DataFrame({'y': ['b', 'c', 'd'], 'z': [4, 5, 6]}) In [3]: df1 Out[3]: x y 0 1 a 1 2 b 2 3 c In [4]: df2 Out[4]: y z 0 b 4 1 c 5 2 d 6 Inner join: Uses the intersection ...