Tutorial by Examples: r

After creating a new model or modifying existing models, you will need to generate migrations for your changes and then apply the migrations to the specified database. This can be done by using the Django's built-in migrations system. Using the manage.py utility when in the project root directory: ...

Units of measure are additional type annotations that can be added to floats or integers. They can be used to verify at compile time that calculations are using units consistently. To define annotations: [<Measure>] type m // meters [<Measure>] type s // seconds [<Measure>] typ...

You can use traits to modify methods of a class, using traits in stackable fashion. The following example shows how traits can be stacked. The ordering of the traits are important. Using different order of traits, different behavior is achieved. class Ball { def roll(ball : String) = println(&q...

We can name our loops and break the specific one when necessary. outerloop: for (var i = 0;i<3;i++){ innerloup: for (var j = 0;j <3; j++){ console.log(i); console.log(j); if (j == 1){ break outerloop; } } } Output: 0 0...

Detailed instructions on getting asp.net-web-api set up or installed.

All looping constructs allow the use of break and continue statements. They affect the immediately surrounding (innermost) loop. Basic Loop Control break terminates the loop: for x in 0..5 { if x > 2 { break; } println!("{}", x); } Output 0 1 2 continue finishes...

While many people think that ^ means the start of a string, it actually means start of a line. For an actual start of string anchor use, \A. The string hello\nworld (or more clearly) hello world Would be matched by the regular expressions ^h, ^w and \Ah but not by \Aw

With IronPython you can access any .net assembly which is compiled using the same or a lower version than the IronPython core. Example: Importing a a .net assembly and class from System import Math Example: Using an imported class: from System import Math print Math.Abs(-123) You can also lo...

Statistical functions in R make heavy use of the so-called Wilkinson-Rogers formula notation1 . When running model functions like lm for the Linear Regressions, they need a formula. This formula specifies which regression coefficients shall be estimated. my_formula1 <- formula(mpg ~ wt) class(...

//1) All attributes should be inherited from System.Attribute //2) You can customize your attribute usage (e.g. place restrictions) by using System.AttributeUsage Attribute //3) You can use this attribute only via reflection in the way it is supposed to be used //4) MethodMetadataAttribute is jus...

[StackDemo(Text = "Hello, World!")] public class MyClass { [StackDemo("Hello, World!")] static void MyMethod() { } }

Method GetCustomAttributes returns an array of custom attributes applied to the member. After retrieving this array you can search for one or more specific attributes. var attribute = typeof(MyClass).GetCustomAttributes().OfType<MyCustomAttribute>().Single(); Or iterate through them forea...

To find out the IP address of your container, use: docker inspect <container id> | grep IPAddress or use docker inspect docker inspect --format '{{ .NetworkSettings.IPAddress }}' ${CID}

Payments Table CustomerPayment_typeAmountPeterCredit100PeterCredit300JohnCredit1000JohnDebit500 select customer, sum(case when payment_type = 'credit' then amount else 0 end) as credit, sum(case when payment_type = 'debit' then amount else 0 end) as debit from payments group by ...

If you need to remove one or more elements from a slice, or if you need to work with a sub slice of another existing one; you can use the following method. Following examples uses slice of int, but that works with all type of slice. So for that, we need a slice, from witch we will remove some ...

Maps in go are not safe for concurrency. You must take a lock to read and write on them if you will be accessing them concurrently. Usually the best option is to use sync.RWMutex because you can have read and write locks. However, a sync.Mutex could also be used. type RWMap struct { sync.RWMut...

Doctrine 2 is easy to install via composer composer require doctrine/orm but it can also be downloaded from http://www.doctrine-project.org/projects/orm.html or from its GitHub project page.

ActionScript 3 can be used by installing the Adobe AIR SDK or Apache Flex SDK or as part Adobe's Animate CC product (formerly known as Flash Professional). Adobe Animate CC is a professional software solution that can be used to create AS3 projects using visual tools - once installed, no further st...

for($i = 0; $i -le 5; $i++){ "$i" } A typical use of the for loop is to operate on a subset of the values in an array. In most cases, if you want to iterate all values in an array, consider using a foreach statement.

ForEach has two different meanings in PowerShell. One is a keyword and the other is an alias for the ForEach-Object cmdlet. The former is described here. This example demonstrates printing all items in an array to the console host: $Names = @('Amy', 'Bob', 'Celine', 'David') ForEach ($Name in $...