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How do you delete a column by name in data.table?
...hod 3 (could then assign to df3,
df3[, !"foo"]
though if you were actually wanting to remove column "foo" from df3 (as opposed to just printing a view of df3 minus column "foo") you'd really want to use Method 1 instead.
(Do note that if you use a method relying on grep() or grepl(), you need ...
Can I mix Swift with C++? Like the Objective-C .mm files
...
No. When you switch from .m to .mm you are actually switching from Objective-C to a different language (which has many subtle differences) called Objective-C++. So you're not really using C++; you're using Objective-C++ which accepts most C++ as input (in the same way tha...
How can I iterate over an enum?
... Two = 9,
Three = 4,
Last
};
This illustrates that an enum is not really meant to iterate through. The typical way to deal with an enum is to use it in a switch statement.
switch ( foo )
{
case One:
// ..
break;
case Two: // intentional fall-through
case Three:
...
How to tell if a string is not defined in a Bash shell script
... not set, you can use:
if [ -z "${VAR+xxx}" ]; then echo VAR is not set at all; fi
if [ -z "$VAR" ] && [ "${VAR+xxx}" = "xxx" ]; then echo VAR is set but empty; fi
You probably can combine the two tests on the second line into one with:
if [ -z "$VAR" -a "${VAR+xxx}" = "xxx" ]; then echo VA...
Is using 'var' to declare variables optional? [duplicate]
...
@codemeit : javascript is full of pitfalls like this, but all in all it's a beautiful and very pleasant language. Don't hate it. Just know the pitfalls and leave them out of your code.
– Stefano Borini
Mar 21 '10 at 1:25
...
JavaScript REST client Library [closed]
Is there a JavaScript library which allow me to perform all the REST operation like ( GET , POST , PUT and DELETE over HTTP or HTTPS )?
...
How does “this” keyword work within a function?
...a certain value, depending on how you invoke the function. This is often called the invocation pattern.
There are four ways to invoke functions in javascript. You can invoke the function as a method, as a function, as a constructor, and with apply.
As a Method
A method is a function that's atta...
Why can I throw null in Java? [duplicate]
...way makes it a bit more obvious as to why this works:
try {
Exception foo = null;
if(false) {
foo = new FileNotFoundException();
} // Oops, forgot to set foo for the true case..
throw foo;
} catch (Exception e){
System.out.println(e instanceof NullPointerException);
...
Remove all child elements of a DOM node in JavaScript
How would I go about removing all of the child elements of a DOM node in JavaScript?
32 Answers
...
Python: reload component Y imported with 'from X import Y'?
... verse (import this from interactive prompt to see the Zen of Python); and all the reasons why namespaces are a honking great idea (immediate local visual clues that the name's being looked up, ease of mocking/injecting in tests, ability to reload, ability for a module to change flexibly by redefini...