Tutorial by Examples: r

We assume a file using ; as a column delimiter. Selecting a specific set of columns only requires a print statement. For instance, the following program selects the columns 3, 4 and 7 from its input: awk -F';' -v 'OFS=;' '{ print $3, $4, $7 }' It is as usual possible to more carefully choose lin...

Given a file using ; as a column delimiter. We compute the median of the values in the second column with the following program, written for GNU awk. The provided input is the list of grades of a student group: gawk -F';' '{ sample[NR] = $2 } END { asort(sample); if(NR % 2 == 1) { p...

There are two main ways to create an axes in matplotlib: using pyplot, or using the object-oriented API. Using pyplot: import matplotlib.pyplot as plt ax = plt.subplot(3, 2, 1) # 3 rows, 2 columns, the first subplot Using the object-oriented API: import matplotlib.pyplot as plt fig = ...

Use import to specify how a namespace from one library is used in the scope of another library. import 'dart:html'; The only required argument to import is a URI specifying the library. For built-in libraries, the URI has the special dart: scheme. For other libraries, you can use a file system p...

Unlike Java, Dart doesn’t have the keywords public, protected, and private. If an identifier starts with an underscore _, it’s private to its library. If you for example have class A in a separate library file (eg, other.dart), such as: library other; class A { int _private = 0; testA()...

If you import two libraries that have conflicting identifiers, then you can specify a prefix for one or both libraries. For example, if library1 and library2 both have an Element class, then you might have code like this: import 'package:lib1/lib1.dart'; import 'package:lib2/lib2.dart' as lib2; /...

If you want to use only part of a library, you can selectively import the library. For example: // Import only foo and bar. import 'package:lib1/lib1.dart' show foo, bar; // Import all names EXCEPT foo. import 'package:lib2/lib2.dart' hide foo;

Deferred loading (also called lazy loading) allows an application to load a library on demand, if and when it’s needed. To lazily load a library, you must first import it using deferred as. import 'package:deferred/hello.dart' deferred as hello; When you need the library, invoke loadLibrary() us...

For example we have WordCountService with countWords method: class WordCountService { def countWords(url: String): Map[String, Int] = { val sparkConf = new SparkConf().setMaster("spark://somehost:7077").setAppName("WordCount")) val sc = new SparkContext(sp...

This command starts up a development server, or dev server, for your Dart web app. The dev server is an HTTP server on localhost that serves up your web app’s assets. Start the dev server from the directory that contains your web app’s pubspec.yaml file: $ cd ~/dart/helloworld $ pub serve Servin...

iex(1)> name = "John" "John" iex(2)> greeting = "Hello, #{name}" "Hello, John" iex(3)> num = 15 15 iex(4)> results = "#{num} item(s) found." "15 item(s) found."

Fortran originally was designed for a fixed format form based on an 80 column punched card: Yes: This is a line of the author's own code These were created on a card punch machine, much like this: Images are original photography by the author The format, as shown on the illustrated sample ca...

There are 2 ways of instantiating prefabs: during design time or runtime. Design time instantiation Instantiating prefabs at design time is useful to visually place multiple instances of the same object (e.g. placing trees when designing a level of your game). To visually instantiate a prefab...

It is a good practice to provide expression string arguments as braced strings. The heading "Double Substitution" outlines important reasons behind the same. The expr command evaluates an operator-based expression string to calculate a value. This string is constructed from the arguments ...

To implement the toString method of an object easily you could use the ToStringBuilder class. Selecting the fields: @Override public String toString() { ToStringBuilder builder = new ToStringBuilder(this); builder.append(field1); builder.append(field2); builder.append(field3...

When the view controller is presented within a tab bar controller, you can access the tab bar controller like this: Swift let tabBarController = viewController.tabBarController Objective-C UITabBarController *tabBarController = self.tabBarController; When the view controller is part on an n...

JavaScript has native conversion from Number to it's String representation for any base from 2 to 36. The most common representation after decimal (base 10) is hexadecimal (base 16), but the contents of this section work for all bases in the range. In order to convert a Number from decimal (base...

The var_dump function allows you to dump the contents of a variable (type and value) for debugging. Example: $array = [3.7, "string", 10, ["hello" => "world"], false, new DateTime()]; var_dump($array); Output: array(6) { [0]=> float(3.7) [1]=> ...

If you want PHP to display runtime errors on the page, you have to enable display_errors, either in the php.ini or using the ini_set function. You can choose which errors to display, with the error_reporting (or in the ini) function, which accepts E_* constants, combined using bitwise operators. P...

C99 Added in the C standard version C99, _Bool is also a native C data type. It is capable of holding the values 0 (for false) and 1 (for true). #include <stdio.h> int main(void) { _Bool x = 1; _Bool y = 0; if(x) /* Equivalent to if (x == 1) */ { puts("T...