Tutorial by Examples: r

To install the software: After the download completes, run the installer. For Windows, the installer executable file has the .exe extension. Double-click the installer file to run it. For Linux platforms, the installer file has the .sh extension. For these platforms, you need to make ...

To run the software: After the download of the platform-independent ZIP file completes, extract it to any folder on your system. Run the executable file located in the netbeans/bin directory. Accept the License Agreement. Click Next. The NetBeans IDE installation starts. Note: If a compatib...

PHP 5.4+ comes with a built-in development server. It can be used to run applications without having to install a production HTTP server such as nginx or Apache. The built-in server is only designed to be used for development and testing purposes. It can be started by using the -S flag: php -S &lt...

The ROLLUP operator is useful in generating reports that contain subtotals and totals. CUBE generates a result set that shows aggregates for all combinations of values in the selected columns. ROLLUP generates a result set that shows aggregates for a hierarchy of values in the selected col...

R contains a Date class, which is created with as.Date(), which takes a string or vector of strings, and if the date is not in ISO 8601 date format YYYY-MM-DD, a formatting string of strptime-style tokens. as.Date('2016-08-01') # in ISO format, so does not require formatting string ## [1] &quot...

Sometimes you will create classes that won't be used in their own right, rather only be extended inside other rule sets. This means that the compiled CSS file will be larger than it needs to be. Placeholder selectors solve this problem. Placeholder selectors are similar to class selectors, but th...

In general OR kills optimization. WHERE a = 12 OR b = 78 cannot use INDEX(a,b), and may or may not use INDEX(a), INDEX(b) via "index merge". Index merge is better than nothing, but only barely. WHERE x = 3 OR x = 5 is turned into WHERE x IN (3, 5) which may use an index with x...

Subqueries come in several flavors, and they have different optimization potential. First, note that subqueries can be either "correlated" or "uncorrelated". Correlated means that they depend on some value from outside the subquery. This generally implies that the subquery mus...

A common problem that leads to an inefficient query goes something like this: SELECT ... FROM a JOIN b ON ... WHERE ... GROUP BY a.id First, the JOIN expands the number of rows; then the GROUP BY whittles it back down the the number of rows in a. There may not be any good c...

Create a testing class in the src/test/scala directory, in a file named HelloWorldSpec.scala. Put this inside the file: import org.scalatest.{FlatSpec, Matchers} class HelloWorldSpec extends FlatSpec with Matchers { "Hello World" should "not be an empty String" in { ...

Detailed instructions on getting cloudkit set up or installed.

// app.module.ts import { NgModule } from '@angular/core'; import { BrowserModule } from '@angular/platform-browser'; import { HttpModule } from '@angular/http'; import { MyRootComponent } from './app.component'; @NgModule({ declarations: [MyRootComponent], imports: [BrowserModule, Ht...

import { platformBrowserDynamic } from '@angular/platform-browser-dynamic'; import { MyModule } from './app.module'; platformBrowserDynamic().bootstrapModule( MyModule ); In this example, MyModule is the module containing your root component. By bootstrapping MyModule your Angul...

This example has two parts - some boilerplate steps for adding Castle Windsor to your WCF service, and then a simple, concrete example to show how we configure and use Windsor's container. That makes the example a little bit long. If you already understand using a DI container then you likely only ...

Prototype: aggregate(zeroValue, seqOp, combOp) Description: aggregate() lets you take an RDD and generate a single value that is of a different type than what was stored in the original RDD. Parameters: zeroValue: The initialization value, for your result, in the desired format. seqOp: ...

Helper yii\helpers\Url provides a set of static methods for managing URLs. This helper may used in views/controllers code. URL to a route: echo Url::to(['post/index']); URL to a route with parameters: echo Url::to(['post/view', 'id' => 100]); anchored URL: echo Url::to(['post/view', 'id...

/** * Checks if a resource exists by sending a HEAD-Request. * @param url The url of a resource which has to be checked. * @return true if the response code is 200 OK. */ public static final boolean checkIfResourceExists(URL url) throws IOException { HttpURLConnection conn = (HttpURLCo...

Let's say you're working on an app called MyTasks, and you want to allow inbound URLs to create a new task with a title and a body. The URL you're designing might look something like this: mytasks://create?title=hello&body=world (Of course, the text and body parameters are used to populate our...

Sometimes we need to perform basic operations like hide/show view based on single value, for that single variable we cannot create model or it is not good practice to create model for that. DataBinding supports basic datatypes to perform those oprations. <layout xmlns:android="http://schema...

First Initialize FirebaseDatabase: FirebaseDatabase database = FirebaseDatabase.getInstance(); Write to your database: // Write a message to the database FirebaseDatabase database = FirebaseDatabase.getInstance(); DatabaseReference myRef = database.getReference("message"); myRef....