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Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
I'm having a little trouble understanding the pass-by-reference properties of data.table . Some operations seem to 'break' the reference, and I'd like to understand exactly what's happening.
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Is gcc 4.8 or earlier buggy about regular expressions?
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<regex> was implemented and released in GCC 4.9.0.
In your (older) version of GCC, it is not implemented.
That prototype <regex> code was added when all of GCC's C++0x support was highly experimental, tracking early C++0x drafts and being ma...
dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
...ies, levels=c(levels(iris$Species), "empty_level"))
# Species is a factor and empty groups are included in the output
iris %>% group_by(Species, .drop=FALSE) %>% tally
#> Species n
#> 1 setosa 50
#> 2 versicolor 50
#> 3 virginica 50
#> 4 empty_level ...
Named colors in matplotlib
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I constantly forget the names of the colors I want to use and keep coming back to this question =)
The previous answers are great, but I find it a bit difficult to get an overview of the available colors from the posted image. I prefer the colors to be grouped with similar colors, ...
Most efficient way of making an if-elif-elif-else statement when the else is done the most?
...e': 3})
for i in xrange(1000000):
the_thing = options[something]
...and note the amount of CPU time they use...
1.py: 160ms
2.py: 170ms
3.py: 110ms
4.py: 100ms
...using the user time from time(1).
Option #4 does have the additional memory overhead of adding a new item for every distinct k...
Equivalent of “continue” in Ruby
In C and many other languages, there is a continue keyword that, when used inside of a loop, jumps to the next iteration of the loop. Is there any equivalent of this continue keyword in Ruby?
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How does type Dynamic work and how to use it?
...se one of these methods it is enough to write a class that extends Dynamic and to implement the methods there:
class DynImpl extends Dynamic {
// method implementations here
}
Furthermore one need to add a
import scala.language.dynamics
or set the compiler option -language:dynamics because t...
What is the meaning of “non temporal” memory accesses in x86
...to be seen by other processors in a timely fashion.
When data is produced and not (immediately) consumed again, the fact that memory store operations read a full cache line first and then modify the cached data is detrimental to performance. This operation pushes data out of the caches which might ...
Redis strings vs Redis hashes to represent JSON: efficiency?
...e cases):
Store the entire object as JSON-encoded string in a single key and keep track of all Objects using a set (or list, if more appropriate). For example:
INCR id:users
SET user:{id} '{"name":"Fred","age":25}'
SADD users {id}
Generally speaking, this is probably the best method in most cas...
FTP/SFTP access to an Amazon S3 Bucket [closed]
...o set up).
Or you can mount the bucket to a file system on a Linux server and access the files using the SFTP as any other files on the server (which gives you greater control).
Or you can just use a (GUI) client that natively supports S3 protocol (what is free).
Managed SFTP Service
In your...