Tutorial by Examples: r

MATLAB allows for several methods to index (access) elements of matrices and arrays: Subscript indexing - where you specify the position of the elements you want in each dimension of the matrix separately. Linear indexing - where the matrix is treated as a vector, no matter its dimensions. That ...

re.findall(r"[0-9]{2,3}", "some 1 text 12 is 945 here 4445588899") # Out: ['12', '945', '444', '558', '889'] Note that the r before "[0-9]{2,3}" tells python to interpret the string as-is; as a "raw" string. You could also use re.finditer() which works in...

Available in the standard library as defaultdict from collections import defaultdict d = defaultdict(int) d['key'] # 0 d['key'] = 5 d['key'] # 5 d = defaultdict(lambda: 'empty') d['key'] # 'empty' d['key'] = 'full' ...

Given some JSON file "foo.json" like: {"foo": {"bar": {"baz": 1}}} we can call the module directly from the command line (passing the filename as an argument) to pretty-print it: $ python -m json.tool foo.json { "foo": { "bar...

To create a variable in Python, all you need to do is specify the variable name, and then assign a value to it. <variable name> = <value> Python uses = to assign values to variables. There's no need to declare a variable in advance (or to assign a data type to it), assigning a value ...

4.0 To uppercase $ v="hello" # Just the first character $ printf '%s\n' "${v^}" Hello # All characters $ printf '%s\n' "${v^^}" HELLO # Alternative $ v="hello world" $ declare -u string="$v" $ echo "$string" HELLO WORLD To l...

In Ruby, there are exactly two values which are considered "falsy", and will return false when tested as a condition for an if expression. They are: nil boolean false All other values are considered "truthy", including: 0 - numeric zero (Integer or otherwise) "&qu...

Number('0') === 0 Number('0') will convert the string ('0') into a number (0) A shorter, but less clear, form: +'0' === 0 The unary + operator does nothing to numbers, but converts anything else to a number. Interestingly, +(-12) === -12. parseInt('0', 10) === 0 parseInt('0', 10) will c...

String(0) === '0' String(0) will convert the number (0) into a string ('0'). A shorter, but less clear, form: '' + 0 === '0'

When ASP.NET handles a request, a thread is assigned from the thread pool and a request context is created. The request context contains information about the current request which can be accessed through the static HttpContext.Current property. The request context for the request is then assigned t...

Most browsers support using color keywords to specify a color. For example, to set the color of an element to blue, use the blue keyword: .some-class { color: blue; } CSS keywords are not case sensitive—blue, Blue and BLUE will all result in #0000FF. Color Keywords Color nameHex valueRGB...

RGB is an additive color model which represents colors as mixtures of red, green, and blue light. In essence, the RGB representation is the decimal equivalent of the Hexadecimal Notation. In Hexadecimal each number ranges from 00-FF which is equivalent to 0-255 in decimal and 0%-100% in percentages....

currentColor returns the computed color value of the current element. Use in same element Here currentColor evaluates to red since the color property is set to red: div { color: red; border: 5px solid currentColor; box-shadow: 0 0 5px currentColor; } In this case, specifyin...

Given a function that accepts a Node-style callback, fooFn(options, function callback(err, result) { ... }); you can promisify it (convert it to a promise-based function) like this: function promiseFooFn(options) { return new Promise((resolve, reject) => fooFn(options, (err, re...

The Problem The abstract equality and inequality operators (== and !=) convert their operands if the operand types do not match. This type coercion is a common source of confusion about the results of these operators, in particular, these operators aren't always transitive as one would expect. &...

The @property decorator can be used to define methods in a class which act like attributes. One example where this can be useful is when exposing information which may require an initial (expensive) lookup and simple retrieval thereafter. Given some module foobar.py: class Foo(object): def __...

In jQuery you can select elements in a page using many various properties of the element, including: Type Class ID Possession of Attribute Attribute Value Indexed Selector Pseudo-state If you know CSS selectors you will notice selectors in jQuery are the same (with minor exceptions). Ta...

InterruptedException is a confusing beast - it shows up in seemingly innocuous methods like Thread.sleep(), but handling it incorrectly leads to hard-to-manage code that behaves poorly in concurrent environments. At its most basic, if an InterruptedException is caught it means someone, somewhere, c...

If you want to use @property to implement custom behavior for setting and getting, use this pattern: class Cash(object): def __init__(self, value): self.value = value @property def formatted(self): return '${:.2f}'.format(self.value) @formatted.setter def ...

The following example shows common AngularJS constructs in one file: <!DOCTYPE html> <html ng-app="myDemoApp"> <head> <style>.started { background: gold; }</style> <script src="https://code.angularjs.org/1.5.8/angular.min.js">&lt...