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The special symbol .SD is available in j of DT[i,j,by], capturing the Subset of Data for each by group surviving the filter, i. .SDcols is a helper. Type ?`special-symbols` for the official docs. A reminder: DT[where, select|update|do, by] syntax is used to work with columns of a data.table. T...

AutoHotkey used to heavily rely on labels until version 1.1.20. It's reliance on labels had very serious disadvantages. The main one being that labels usually execute in the global scope meaning that any variable defined within a label will be globally available. This sounds great until you realiz...

There is a nice chapter on the matter in Efficient R programming

This section provides an overview of what coffeescript is, and why a developer might want to use it. It should also mention any large subjects within coffeescript, and link out to the related topics. Since the Documentation for coffeescript is new, you may need to create initial versions of thos...

For ease of readability, keep all declarations indented one level from their selector, and the closing curly brace on its own line. Add a single space after selectors and colons, and always place a semicolon after the final declaration. Good p { color: maroon; font-size: 16px; } ...

count(node-set) functionreturnscounttotal number of nodes in the node set We can use this in combination of other functions and axes to suit our needs.

A note about implemeting both methods When both methods are implemented, it's somewhat common to have a __str__ method that returns a human-friendly representation (e.g. "Ace of Spaces") and __repr__ return an eval-friendly representation. In fact, the Python docs for repr() note ex...