Tutorial by Examples: in

Adding and modifying columns

DT[where, select|update|do, by] syntax is used to work with columns of a data.table. The "where" part is the i argument The "select|update|do" part is the j argument These two arguments are usually passed by position instead of by name. Our example data below is mtcars =...

R Language • data.table

Why are there two build.gradle files in an Android Studio project?

<PROJECT_ROOT>\app\build.gradle is specific for app module. <PROJECT_ROOT>\build.gradle is a "Top-level build file" where you can add configuration options common to all sub-projects/modules. If you use another module in your project, as a local library you would have another...

Android • Gradle for Android

Creating a new program using .NET Core

First install the .NET Core SDK by going through the installation instructions for the platform of your choice: Windows OSX Linux Docker After the installation has completed, open a command prompt, or terminal window. Create a new directory with mkdir hello_world and change into the ne...

C# Language • Getting started with C# Language

Using the where statement in a switch

The where statement may be used within a switch case match to add additional criteria required for a positive match. The following example checks not only for the range, but also if the number is odd or even: switch (temperature) { case 0...49 where temperature % 2 == 0: print(&quot...

Swift Language • Switch

Getting the string representation of a Guid

A string representation of a Guid can be obtained by using the built in ToString method string myGuidString = myGuid.ToString(); Depending on your needs you can also format the Guid, by adding a format type argument to the ToString call. var guid = new Guid("7febf16f-651b-43b0-a5e3-0da8da4...

C# Language • Guid

Most Common Real Life Key Value Coding Example

Key Value Coding is integrated into NSObject using NSKeyValueCoding protocol. What this means? It means that any id object is capable of calling valueForKey method and its various variants like valueForKeyPath etc. ' It also means that any id object can invoke setValue method and its various vari...

Objective-C Language • Key Value Coding / Key Value Observing

Reducing the Capacity of a Vector

A std::vector automatically increases its capacity upon insertion as needed, but it never reduces its capacity after element removal. // Initialize a vector with 100 elements std::vector<int> v(100); // The vector's capacity is always at least as large as its size auto const old_capacity...

C++ • std::vector

Installation or Setup

Google Apps Script does not require setup or installation. The only requirement is a Google Account. A Gmail account works as well as a Google Apps for Work/Education/Government account. You can create a new Google account by going to accounts.google.com Start your first script by going to script.g...

google-apps-script • Getting started with google-apps-script

Declaring a property

At its simplest, a property is a function which returns a Bool. prop_reverseDoesNotChangeLength xs = length (reverse xs) == length xs A property declares a high-level invariant of a program. The QuickCheck test runner will evaluate the function with 100 random inputs and check that the result is...

Haskell Language • QuickCheck

Using a template object

You can use an instance of an object to form your parameters public class SearchParameters { public string SearchString { get; set; } public int Page { get; set; } } var template= new SearchParameters { SearchString = "Dapper", Page = 1 }; var p = new DynamicParameters...

Dapper.NET • Dynamic Parameters

Joining Strings with a delimiter

Java SE 8 An array of strings can be joined using the static method String.join(): String[] elements = { "foo", "bar", "foobar" }; String singleString = String.join(" + ", elements); System.out.println(singleString); // Prints "foo + bar + foobar&qu...

Java Language • Strings

Formatting Dates

To format Dates we use the format(date, format="%Y-%m-%d") function with either the POSIXct (given from as.POSIXct()) or POSIXlt (given from as.POSIXlt()) d = as.Date("2016-07-21") # Current Date Time Stamp format(d,"%a") # Abbreviated Weekday ## [1] &qu...

R Language • The Date class

Formatting and printing date-time objects

# test date-time object options(digits.secs = 3) d = as.POSIXct("2016-08-30 14:18:30.58", tz = "UTC") format(d,"%S") # 00-61 Second as integer ## [1] "30" format(d,"%OS") # 00-60.99… Second as fractional ## [1] "30.579" for...

R Language • Date-time classes (POSIXct and POSIXlt)

Parsing strings into date-time objects

The functions for parsing a string into POSIXct and POSIXlt take similar parameters and return a similar-looking result, but there are differences in how that date-time is stored; see "Remarks." as.POSIXct("11:38", # time string format = "...

R Language • Date-time classes (POSIXct and POSIXlt)

Getting Started: Hello world!

Creating an HTML document and enabling knockout.js Create an HTML file and include knockout.js via a <script> tag. <!DOCTYPE html> <html> <head> <title>Hello world! (knockout.js)</title> </head> <body> <script src="https://cdnjs...

knockout.js • Getting started with knockout.js

Checking a single property

The quickCheck function tests a property on 100 random inputs. ghci> quickCheck prop_reverseDoesNotChangeLength +++ OK, passed 100 tests. If a property fails for some input, quickCheck prints out a counterexample. prop_reverseIsAlwaysEmpty xs = reverse xs == [] -- plainly not true for all ...

Haskell Language • QuickCheck

INSERT on specific columns

To do an insert on specific columns (as opposed to all of them) you must specify the columns you want to update. INSERT INTO USERS (FIRST_NAME, LAST_NAME) VALUES ('Stephen', 'Jiang'); This will only work if the columns that you did not list are nullable, identity, timestamp data type or compute...

Microsoft SQL Server • INSERT INTO

INSERT multiple rows of data

To insert multiple rows of data in SQL Server 2008 or later: INSERT INTO USERS VALUES (2, 'Michael', 'Blythe'), (3, 'Linda', 'Mitchell'), (4, 'Jillian', 'Carson'), (5, 'Garrett', 'Vargas'); To insert multiple rows of data in earlier versions of SQL Server, use "UNION ALL" like so: ...

Microsoft SQL Server • INSERT INTO

INSERT a single row of data

A single row of data can be inserted in two ways: INSERT INTO USERS(Id, FirstName, LastName) VALUES (1, 'Mike', 'Jones'); Or INSERT INTO USERS VALUES (1, 'Mike', 'Jones'); Note that the second insert statement only allows the values in exactly the same order as the table columns whereas in...

Microsoft SQL Server • INSERT INTO

Copying contents from one slice to another slice

If you wish to copy the contents of a slice into an initially empty slice, following steps can be taken to accomplish it- Create the source slice: var sourceSlice []interface{} = []interface{}{"Hello",5.10,"World",true} Create the destination slice, with: Length =...

Go • Slices