Tutorial by Examples: u

This is very common, you memorize a path to a file or folder, you open up Vim and try to write what you've just memorized, but you are not 100% sure it's correct, so you close the editor and start over. When you want the path completion feature, and you have a file /home/ubuntu/my_folder/my_file a...

To delete some lines of text when you don't know exact number of lines to delete, you try 10dd , 5dd , 3dd until you remove all the lines. Relative line numbers solves this problem, suppose we have a file containing : sometimes, you see a block of text. You want to remove it but you cannot d...

The following command executes :command on lines 23 to 56: :23,56command NB: Ranges are inclusive by default.

In the following command the range starts 6 lines above the current line and ends 3 lines below: :-6,+3command

. represents the current line but it can also be omitted entirely. $ represents the last line. % represents the whole buffer, it is a shortcut for 1,$. The two commands below execute :command on every file from the current line to the last line: :.,$command :,$command The command below e...

SELECT DISTINCT ContinentCode FROM Countries; This query will return all DISTINCT (unique, different) values from ContinentCode column from Countries table ContinentCodeOCEUASNAAF SQLFiddle Demo

* on the word you want to substitute. :%s//replacement/g, leaving the find pattern empty.

Using built-in colormaps is as simple as passing the name of the required colormap (as given in the colormaps reference) to the plotting function (such as pcolormesh or contourf) that expects it, usually in the form of a cmap keyword argument: import matplotlib.pyplot as plt import numpy as np ...

Apart from the built-in colormaps defined in the colormaps reference (and their reversed maps, with '_r' appended to their name), custom colormaps can also be defined. The key is the matplotlib.cm module. The below example defines a very simple colormap using cm.register_cmap, containing a single c...

The original default colourmap of MATLAB (replaced in version R2014b) called jet is ubiquitous due to its high contrast and familiarity (and was the default of matplotlib for compatibility reasons). Despite its popularity, traditional colormaps often have deficiencies when it comes to representing d...

# config/locales/en.yml en: stackoverflow: header: title_html: "Use <strong>I18n</strong> with Tags & Symbols" Note the addition of extra _html after the name title. And in Views, # ERB <h2><%= t(:title_html, scope: [:stackoverflow, :heade...

We have a Product model and we want to group them by their category. Product.select(:category).group(:category) This will query the database as follows: SELECT "product"."category" FROM "product" GROUP BY "product"."category" Make sure that t...

If you want to remove duplicates from a result, you can use .distinct(): Customers.select(:country).distinct This queries the database as follows: SELECT DISTINCT "customers"."country" FROM "customers" .uniq() has the same effect. With Rails 5.0 it got deprecate...

In elm, a function's value is computed when the last argument is applied. In the example below, the diagnostic from log will be printed when f is invoked with 3 arguments or a curried form of f is applied with the last argument. import String import Debug exposing (log) f a b c = String.join &...

When reading tabular datasets with the read.* functions, R automatically looks for missing values that look like "NA". However, missing values are not always represented by NA. Sometimes a dot (.), a hyphen(-) or a character-value (e.g.: empty) indicates that a value is NA. The na.strings ...

Install the stable release from CRAN: install.packages("data.table") Or the development version from github: install.packages("data.table", type = "source", repos = "http://Rdatatable.github.io/data.table") To revert from devel to CRAN, the ...

This example will show how to get the mouse position relative to the canvas, such that (0,0) will be the top-left hand corner of the HTML5 Canvas. The e.clientX and e.clientY will get the mouse positions relative to the top of the document, to change this to be based on the top of the canvas we subt...

If you want to detect when your user starts or finishes an activity such as walking, running, or any other activity of the DetectedActivityFence class, you can create a fence for the activity that you want to detect, and get notified when your user starts/finishes this activity. By using a Broadcast...

The symbol NA is for a logical missing value: class(NA) #[1] "logical" This is convenient, since it can easily be coerced to other atomic vector types, and is therefore usually the only NA you will need: x <- c(1, NA, 1) class(x[2]) #[1] "numeric" If you do need a s...

It is always recommend to go to the LLVM official website and follow the installation guides depending on your OS. If you are working on posix then in short you have to add one of the official LLVM package repositories. For example if you work on Ubuntu Xenial (16.04) you add a deb and deb-src entr...