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How do you delete a column by name in data.table?
...
Any of the following will remove column foo from the data.table df3:
# Method 1 (and preferred as it takes 0.00s even on a 20GB data.table)
df3[,foo:=NULL]
df3[, c("foo","bar"):=NULL] # remove two columns
myVar = "foo"
df3[, (myVar):=NULL] # lookup myVar contents...
What is the instanceof operator in JavaScript?
... type.
Here are some good examples and here is an example taken directly from Mozilla's developer site:
var color1 = new String("green");
color1 instanceof String; // returns true
var color2 = "coral"; //no type specified
color2 instanceof String; // returns false (color2 is not a String object)
...
ICollection Vs List in Entity Framework
...
ICollection differs from IEnumerable in that you can actually add items to the collection, whereas with IEnumerable you can't. So in your POCO classes, for instance, you want to use ICollection if you intend to allow the collection to be added t...
Is there a list of screen resolutions for all Android based phones and tablets? [closed]
... with different aspect ratios
The different aspect ratios seen above are (from most square; h/w):
1:1 1.0 <- rare for phone; common for watch
4:3 1.3333 <- matches iPad (when portrait)
3:2 1.5000
38:25 1.5200
14:9 1.5556 <- rare
25:16 1.5625
8:5 1.6000 <- ...
When should I choose Vector in Scala?
...ecomposition in head/tail is about 10 times faster on lists and generation from a traversable is about 2 times faster for vectors. (This is probably, because Vector can allocate arrays of 32 elements at once when you build it up using a builder instead of prepending or appending elements one by one)...
Find a Git branch containing changes to a given file
...57 branches contain a change which includes that filename. Branches start from the oldest revision reachable on that branch, even if that revision existed before you created the branch (the branch is in some senses retroactively created). I think you need to define your problem better. Do you kno...
How to create a generic array in Java?
...t(int s) {
a = new Foo[s];
}
...
}
All of this results from a known, and deliberate, weakness of generics in Java: it was implemented using erasure, so "generic" classes don't know what type argument they were created with at run time, and therefore can not provide type-safety un...
Install gitk on Mac
...blem and solved it as follows:
Download the official git package for Mac from http://git-scm.com/download/mac
Install the package. This places all the binaries in /usr/local/git/bin.
Optionally run the included script to make gitk accessible outside of terminals
Either add /usr/local/git/bin to yo...
Multiple returns from a function
...t in str_replace, $matches in preg_match). This might feel quite different from returning multiple values, but it is worth at least knowing about.
A third method is to use an object to hold the different values you need. This is more typing, so it's not used quite as often as the two methods above....
Best way to implement request throttling in ASP.NET MVC?
...ervers are behind a load balancer, as all of the traffic will appear to be from the same IP address. Unless I am missing something obvious...
– Dscoduc
Sep 30 '19 at 21:35
ad...