Tutorial by Examples: ha

When factors are created with defaults, levels are formed by as.character applied to the inputs and are ordered alphabetically. charvar <- rep(c("W", "n", "c"), times=c(17,20,14)) f <- factor(charvar) levels(f) # [1] "c" "n" "W" ...

Step 1. In your host machine (Windows/Linux/OSX), create an empty dir my_project. Step 2. Create a file named Vagrantfile with this: Vagrant.configure("2") do |config| config.vm.box = "gbarbieru/xenial" #An Ubuntu 16.04 based image config.vm.hostname = "my_project&...

// Usage: drawLineWithArrows(50,50,150,50,5,8,true,true); // x0,y0: the line's starting point // x1,y1: the line's ending point // width: the distance the arrowhead perpendicularly extends away from the line // height: the distance the arrowhead extends backward from the endpoint // arrow...

// Usage: var p0={x:50,y:100}; var p1={x:100,y:0}; var p2={x:200,y:200}; var p3={x:300,y:100}; cubicCurveArrowHeads(p0, p1, p2, p3, 15, true, true); quadraticCurveArrowHeads(p0, p1, p2, 15, true, true); // or use defaults true for both ends with arrow heads cubicCurveArrowHeads(p0, p...

One more PCRE modifier that allows the use of duplicate named groups. NOTE: only inline version is supported - (?J), and must be placed at the start of the pattern. If you use /(?J)\w+-(?:new-(?<val>\w+)|\d+-empty-(?<val>[^-]+)-collection)/ the "val" group values will be ...

Reading invalid UTF-8 When reading UTF-8 encoded data, it is important to be aware of the fact the UTF-8 encoded data can be invalid or malformed. Such data should usually not be accepted by your program (unless you know what you are doing). When unexpectedly encountering malformed data, different ...

Java EE stands for Java Enterprise Edition. Java EE extends the Java SE (which stands for Java Standard Edition). Java EE is a set of technologies and related specifications that are oriented towards the development of large-scale enterprise applications. Java EE is developed in a community driven p...

Since an enum can be cast to and from its underlying integral type, the value may fall outside the range of values given in the definition of the enum type. Although the below enum type DaysOfWeek only has 7 defined values, it can still hold any int value. public enum DaysOfWeek { Monday = 1...

Darken #demo { @refcolor: #f0b9b8; background: @refcolor; border: 1px solid darken(@refcolor, 25%); } The above code makes use of the darken() function to set the border color as a shade that is 25% darker than the reference color (which is also the background color). Less compiler ca...

Loading the SharePoint Snapin can be done using the following: Add-PSSnapin "Microsoft.SharePoint.PowerShell" This only works in the 64bit version of PowerShell. If the window says "Windows PowerShell (x86)" in the title you are using the incorrect version. If the Snap-In is a...

When deriving Serialize and Deserialize implementations for structs with generic type parameters, most of the time Serde is able to infer the correct trait bounds without help from the programmer. It uses several heuristics to guess the right bound, but most importantly it puts a bound of T: Seriali...

Less allows the usage of the parent selector (&) anywhere in a complex selector and thus allows changing styles when the current element is within another element which gives it a different context: For example, in the below code the parent selector is placed at the end and thus it actually be...

Functions are found by first collecting a set of "associated classes" and "associated namespaces" that include one ore more of the following, depending on the argument type T. First, let us show the rules for classes, enumeration and class template specialization names. If T i...

The change the definition of a db column, the query below can be used for example, if we have this db schema users ( firstname varchar(20), lastname varchar(20), age char(2) ) To change the type of age column from char to int, we use the query below: ALTER TABLE users CHANGE age...

Note: in the subsequent passages, the terms hash map and hash table are used interchangeably and refer to the same concept, namely, a data structure providing efficient key lookup through use of an internal hash function. Introduction Although R does not provide a native hash table structure, simi...

This tutorial will guide you through the process from scratch. Please note some preliminary notes about this particular setup, useful in case that you already have some requested package: Is needed a version of php >=5.0 (I had troubles with php 7.0) Is requested any version of perl Is need...

A Haskell's Functor allows one to map any type a (an object of Hask) to a type F a and also map a function a -> b (a morphism of Hask) to a function with type F a -> F b. This corresponds to a Category Theory definition in a sense that functor preserves basic category structure. A monoidal ca...

To execute a function within a loop in node.js, it's fine to use a for loop for short loops. But the loop is long, using for loop will increase the time of processing which might cause the node process to hang. In such scenarios, you can use: asycn.times function recursiveAction(n, callback) { ...

When we want to handle array of data, its better to use async.each. When we want to perform something with all data & want to get the final callback once everything is done, then this method will be useful. This is handled in parallel way. function createUser(userName, callback) { //creat...

# example data DT = data.table(id = c(1,2,2,3,3,3))[, v := LETTERS[.I]][] To deal with "duplicates," combine counting rows in a group and subsetting rows by group. Keep one row per group Aka "drop duplicates" aka "deduplicate" aka "uniquify." unique(DT,...