Tutorial by Examples: b

# example data DT = data.table(Titanic) Suppose we want to see each class only if a majority survived: DT[, if (sum(N[Survived=="Yes"]) > sum(N[Survived=="No"]) ) .SD, by=Class] # Class Sex Age Survived N # 1: 1st Male Child No 0 # 2: 1st Fema...

A quick note before actually installing RabbitMQ: Ubuntu 14.04's Erlang packages have issues if you are using SSL with RabbitMQ, so you'll need to install a newer version than what the Ubuntu package maintainers provide, so use the binaries at https://www.erlang-solutions.com/resources/download.html...

Monotonic predicates can be debugged by applying declarative reasoning. In pure Prolog, a programming mistake can lead to one or all of the following phenomena: the predicate incorrectly succeeds in a case where it should fail the predicate incorrectly fails in a case where it should succeed t...

It is sometimes argued that, for the sake of efficiency, we must accept the use of non-monotonic constructs in real-world Prolog programs. There is no evidence for this. Recent research indicates that the pure monotonic subset of Prolog may not only be sufficient to express most real-world programs...

To interact with WebElements in a webpage, first we need to identify the location of the element. By is the keyword available in selenium. You can locate the elements By.. By ID By Class Name By TagName By Name By Link Text By Partial Link Text By CSS Selector By XPath Using JavaScript ...

Option Compare Binary Binary comparison makes all checks for string equality within a module/class case sensitive. Technically, with this option, string comparisons are performed using sort order of the binary representations of each character. A < B < E < Z < a < b < e < z ...

Option Base is used to declare the default lower bound of array elements. It is declared at module level and is valid only for the current module. By default (and thus if no Option Base is specified), the Base is 0. Which means that the first element of any array declared in the module has an index...

In VB.NET, every variable must be declared before it is used (If Option Explicit is set to On). There are two ways of declaring variables: Inside a Function or a Sub: Dim w 'Declares a variable named w of type Object (invalid if Option Strict is On) Dim x As String 'Declares a variable named ...

Dim flags = BindingFlags.Static Or BindingFlags.Public Or BindingFlags.Instance Dim members = GetType(String).GetMembers(flags) For Each member In members Console.WriteLine($"{member.Name}, ({member.MemberType})") Next

To get more information about any git command – i.e. details about what the command does, available options and other documentation – use the --help option or the help command. For example, to get all available information about the git diff command, use: git diff --help git help diff Similarl...

Python 3.x3.2 accumulate yields a cumulative sum (or product) of numbers. >>> import itertools as it >>> import operator >>> list(it.accumulate([1,2,3,4,5])) [1, 3, 6, 10, 15] >>> list(it.accumulate([1,2,3,4,5], func=operator.mul)) [1, 2, 6, 24, 120] ...

Ionic 1.2 officially supports deployment as a website If you're not using any Cordova plugins then there is no problem (if you really wish to) to upload the contents of the www folder to your server, and woila - you'll have the same app. However, it is important to note that Ionic 1 never intended...

Creating a separate instance of the WP_Query object is easy: $query_args = array( 'post_type' => 'post', 'post_per_page' => 10 ); $my_query = new WP_Query($query_args); if( $my_query->have_posts() ): while( $my_query->have_posts...

A Cordova application runs as a website on a WebView component within the native mobile platform. Debugging a cordova application can therefore be done by utilizing your favourite browsers development tools. The following steps are needed to hook the application, running on the device, to the Chrome...

Enable and configure the experimental Gradle plugin to improve AndroidStudio's NDK support. Check that you fulfill the following requirements: Gradle 2.10 (for this example) Android NDK r10 or later Android SDK with build tools v19.0.0 or later Configure MyApp/build.gradle file Edit the dep...

You can use method chaining while working with JSONObject and JSONArray. JSONObject example JSONObject obj = new JSONObject();//Initialize an empty JSON object //Before: {} obj.put("name","Nikita").put("age","30").put("isMarried","true&quot...

When to use abstract classes: To implement the same or different behaviour among multiple related objects When to use interfaces: to implement a contract by multiple unrelated objects Abstract classes create "is a" relations while interfaces provide "has a" capability. This c...

sudo apt-add-repository ppa:brightbox/ruby-ng Hit Enter to confirm sudo apt-get update Then you can install your ruby version of choice (the ppa supports ruby2.0 ruby2.1 ruby2.2 ruby2.3 and legacy versions ruby1.8 ruby1.9.1) Don't forget to include the respective -dev package for your version. Ot...

With implicit keys: key: value another key: - some - more - values [1, 2, 3]: last value, which has a flow style key With implicit and explicit keys: ? key : value another key: - some - more - values ? [1, 2, 3] : last value, which has a flow style key key, another ...

To see all the facts involving the le relation from the prelude: Coq < Search le. le_n: forall n : nat, n <= n le_S: forall n m : nat, n <= m -> n <= S m ... max_l: forall n m : nat, m <= n -> Nat.max n m = n max_r: forall n m : nat, n <= m -> Nat.max n m = m ... ...