Tutorial by Examples: e

Use anonymous functions with apply

apply is used to evaluate a function (maybe an anonymous one) over the margins of an array or matrix. Let's use the iris dataset to illustrate this idea. The iris dataset has measurements of 150 flowers from 3 species. Let's see how this dataset is structured: > head(iris) Sepal.Length Sep...

R Language • *apply family of functions (functionals)

Cloning an existing table

A table can be replicated as follows: CREATE TABLE ClonedPersons LIKE Persons; The new table will have exactly the same structure as the original table, including indexes and column attributes. As well as manually creating a table, it is also possible to create table by selecting data from anot...

MySQL • Table Creation

Array definition

Dim array(9) As Integer ' Defines an array variable with 10 Integer elements (0-9). Dim array = New Integer(10) {} ' Defines an array variable with 11 Integer elements (0-10) 'using New. Dim array As Integer() = {1, 2, 3, 4} ' Defines an Integer array variable a...

Visual Basic .NET Language • Array

Enum Polymorphism Pattern

When a method need to accept an "extensible" set of enum values, the programmer can apply polymorphism like on a normal class by creating an interface which will be used anywere where the enums shall be used: public interface ExtensibleEnum { String name(); } This way, any enum t...

Java Language • Enums

Reversing Strings

2.2 let aString = "This is a test string." // first, reverse the String's characters let reversedCharacters = aString.characters.reverse() // then convert back to a String with the String() initializer let reversedString = String(reversedCharacters) print(reversedString) // &q...

Swift Language • Strings and Characters

Adding the Doctype

The <!DOCTYPE> declaration should always be included at the top of the HTML document, before the <html> tag. 5 See HTML 5 Doctype for details on the HTML 5 Doctype. <!DOCTYPE html> 4.01 See HTML 4.01 Doctypes for details on how these types differ from each other. Stri...

HTML • Doctypes

Get the list of all databases on a server

Method 1: Below query will be applicable for SQL Server 2000+ version (Contains 12 columns) SELECT * FROM dbo.sysdatabases Method 2: Below query extract information about databases with more informations (ex: State, Isolation, recovery model etc.) Note: This is a catalog view and will be availa...

Microsoft SQL Server • Retrieve information about the database

Install Yii2 advanced in ubuntu

First we need to install composer. Steps to install composer Install Composer. curl -sS https://getcomposer.org/installer | php Now change directory: sudo mv composer.phar /usr/local/bin/composer Check composer working composer Now Composer installed. There two ways to install Yii2 adv...

yii2 • Getting started with yii2

Interfaces

Introduction Interfaces are definitions of the public APIs classes must implement to satisfy the interface. They work as "contracts", specifying what a set of subclasses does, but not how they do it. Interface definition is much alike class definition, changing the keyword class to inter...

PHP • Classes and Objects

Manipulating Array Elements

Adding elements: [1, 2, 3] << 4 # => [1, 2, 3, 4] [1, 2, 3].push(4) # => [1, 2, 3, 4] [1, 2, 3].unshift(4) # => [4, 1, 2, 3] [1, 2, 3] << [4, 5] # => [1, 2, 3, [4, 5]] Removing elements: array = [1, 2, 3, 4] array.pop # => 4 array # => [1, 2, 3] ...

Ruby Language • Arrays

while, until

A while loop executes the block while the given condition is met: i = 0 while i < 5 puts "Iteration ##{i}" i +=1 end An until loop executes the block while the conditional is false: i = 0 until i == 5 puts "Iteration ##{i}" i +=1 end

Ruby Language • Control Flow

Merge with a commit

Default behaviour is when the merge resolves as a fast-forward, only update the branch pointer, without creating a merge commit. Use --no-ff to resolve. git merge <branch_name> --no-ff -m "<commit message>"

Git • Merging

Print statement vs. Print function

In Python 2, print is a statement: Python 2.x2.7 print "Hello World" print # print a newline print "No newline", # add trailing comma to remove newline print >>sys.stderr, "Error" # print to stderr print("hello"...

Python Language • Incompatibilities moving from Python 2 to Python 3

Installation and Setup

Prerequisites and Requirements for Magento Community Edition 1.9 Hosting Apache 2.x ( with mod_rewrite ) or Nginx 1.7.x Due to the demands of processing Magento operations, it is recommended that you install Magento on a server with at least 2 GB of RAM. This will ensure that all of the s...

magento • Getting started with magento

Intent URI

This example shows, how to start intent from browser: <a href="intent://host.com/path#Intent;package=com.sample.test;scheme=yourscheme;end">Start intent</a> This intent will start app with package com.sample.test or will open google play with this package. Also this intent...

Android • Intent

Obtaining OpenGL

One of the most common misconceptions about OpenGL is, that it were a library that could be installed from 3rd party sources. This misconception leads to many questions in the form "how to I install OpenGL" or "where to download the OpenGL SDK". This is not how OpenGL finds the ...

opengl • Getting started with opengl

Using Entity Framework from C# (Code First)

Code first allows you to create your entities (classes) without using a GUI designer or a .edmx file. It is named Code first, because you can create your models first and Entity framework will create database according to mappings for you automatically. Or you can also use this approach with existin...

Entity Framework • Getting started with Entity Framework

Installation or Setup

Windows If you have Visual Studio (any version including express and community) installed, F# should already be included. Just choose F# as the language when you create a new project. Or see http://fsharp.org/use/windows/ for more options. OS X Xamarin Studio supports F#. Alternately, you could u...

F# • Getting started with F#

Installation/Setup

Downloading: Download Bootstrap directly or clone, etc. from the GitHub repository Download your customized version of Bootstrap from official docs Install with bower: bower install bootstrap Install with npm: npm install bootstrap Install with composer: composer require twbs/bootstrap The...

twitter-bootstrap • Getting started with twitter-bootstrap

Read value of pointer that was freed

Even just reading the value of a pointer that was freed (i.e. without trying to dereference the pointer) is undefined behavior(UB), e.g. char *p = malloc(5); free(p); if (p == NULL) /* NOTE: even without dereferencing, this may have UB */ { } Quoting ISO/IEC 9899:2011, section 6.2.4 §2: ...

C Language • Undefined behavior