Tutorial by Examples: r

To create a NuGet package from a project, run this command from a directory that contains project.json: dotnet pack The resulting .nupkg file will be named and versioned according to the properties in project.json. If there are multiple frameworks targeted in the project file, the package will s...

Running dotnet test from inside a folder that contains a test project will launch the test runner. The test runner will discover and run the tests in the project. To be compatible with dotnet test, the project.json file must contain a testRunner property and a dependency on a compatible test runner...

Command line scripts inside python packages are common. You can organise your package in such a way that when a user installs the package, the script will be available on their path. If you had the greetings package which had the command line script hello_world.py. greetings/ greetings/ ...

C++11 threading primitives are still relatively low level. They can be used to write a higher level construct, like a thread pool: C++14 struct tasks { // the mutex, condition variable and deque form a single // thread-safe triggered queue of tasks: std::mutex m; std::condition_variab...

The Composite pattern is a design pattern that allows to treat a group of objects as a single instance of an object. It is one of the Gang of Four's structural design patterns. Example below demonstrate how Composite can be used to log to multiple places using single Log invocation. This approach a...

As of Java 8, there are default methods on the Map.Entry interface to allow sorting of map iterations. Java SE 8 Map<String, Integer> numberOfEmployees = new HashMap<>(); numberOfEmployees.put("executives", 10); numberOfEmployees.put("human ressources", 32); numb...

MySQL provides the following arithmetic operators OperatorNameExample+AdditionSELECT 3+5; -> 8 SELECT 3.5+2.5; -> 6.0 SELECT 3.5+2; -> 5.5-SubtractionSELECT 3-5; -> -2*MultiplicationSELECT 3 * 5; -> 15/DivisionSELECT 20 / 4; -> 5 SELECT 355 / 113; -> 3.1416 SELECT 10.0 / 0; -...

Angles are in Radians, not Degrees. All computations are done in IEEE 754 64-bit floating point. All floating point computations are subject to small errors, known as machine ε (epsilon) errors, so avoid trying to compare them for equality. There is no way to avoid these errors when using floating p...

Round a decimal number to an integer value For exact numeric values (e.g. DECIMAL): If the first decimal place of a number is 5 or higher, this function will round a number to the next integer away from zero. If that decimal place is 4 or lower, this function will round to the next integer value cl...

To raise a number x to a power y, use either the POW() or POWER() functions SELECT POW(2,2); => 4 SELECT POW(4,2); => 16

Use the SQRT() function. If the number is negative, NULL will be returned SELECT SQRT(16); -> 4 SELECT SQRT(-3); -> NULL

Generate a random number To generate a pseudorandom floating point number between 0 and 1, use the RAND() function Suppose you have the following query SELECT i, RAND() FROM t; This will return something like this iRAND()10.619143887068220.9384516830914230.83482678498591 Random Number in a r...

Mixins are a sort of class that is used to "mix in" extra properties and methods into a class. This is usually fine because many times the mixin classes don't override each other's, or the base class' methods. But if you do override methods or properties in your mixins this can lead to une...

To install and load the current stable version of ggplot2 for your R installation use: # install from CRAN install.packages("ggplot2") To install the development version from github use # install.packages("devtools") devtools::install_github("hadley/ggplot2") ...

public class ConnectSocketExample { private int HTTP_PORT = 80; /** * example method to create unconnected socket * then connect to it * at end return connected socket * * @param httpHostName - endpoint host name fot socket connection * @throws IOEx...

/** * we reuse a class written in example: * http://stackoverflow.com/documentation/sockets/2876/introduction-to-sockets#t=201607262114505531351 * pleas to familiar with it first to continue with this one **/ public class WriteToSocketExample extends ConnectSocketExample { private ...

A macro is a series of keystrokes meant to be "played back" by Vim without any delay. Macros can be stored in registers or variables, bound to keys, or executed on the command line. Here is a simple macro that uppercases the third word on a line: 0wwgUiw That macro could be recorded i...

5.1 This Example demonstrates how to automatically assign a value to each entry in an enum list. This will prevent two enums from having the same value by mistake. NOTE: Object.freeze browser support var testEnum = function() { // Initializes the enumerations var enumList = [ &q...

import java.util.Scanner; Scanner s = new Scanner(System.in); int number = s.nextInt(); If you want to read an int from the command line, just use this snippet. First of all, you have to create a Scanner object, that listens to System.in, which is by default the Command Line, when you start ...

SpriteKit functionality can be implemented in a subclass of SKScene. For example, a game may implement the main game functionality within an SKScene subclass called GameScene. In Swift: import SpriteKit class GameScene: SKScene { override func didMoveToView(view: SKView) { /* Co...