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What does .SD stand for in data.table in R
...his is your data.table:
DT = data.table(x=rep(c("a","b","c"),each=2), y=c(1,3), v=1:6)
setkey(DT, y)
DT
# x y v
# 1: a 1 1
# 2: b 1 3
# 3: c 1 5
# 4: a 3 2
# 5: b 3 4
# 6: c 3 6
Doing this may help you see what .SD is:
DT[ , .SD[ , paste(x, v, sep="", collapse="_")], by=y]
# y V1
# 1...
How do you split a list into evenly sized chunks?
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How to delete duplicates on a MySQL table?
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216
this removes duplicates in place, without making a new table
ALTER IGNORE TABLE `table_name` A...
character showing up in files. How to remove them?
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13 Answers
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Find merge commit which include a specific commit
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Batch script loop
I need to execute a command 100-200 times, and so far my research indicates that I would either have to copy/paste 100 copies of this command, OR use a for loop, but the for loop expects a list of items, hence I would need 200 files to operate on, or a list of 200 items, defeating the point.
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Get all non-unique values (i.e.: duplicate/more than one occurrence) in an array
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What belongs in an educational tool to demonstrate the unwarranted assumptions people make in C/C++?
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The order of evaluation of subexpressions, including
the arguments of a function call and
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How do I specify multiple targets in my podfile for my Xcode project?
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CocoaPods 1.0 has changed the syntax for this. It now looks like this:
def shared_pods
pod 'SSKeychain', '~> 0.1.4'
pod 'INAppStoreWindow', :head
pod 'AFNetworking', '1.1.0'
pod 'Reachability', '~> 3.1.0'
po...