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Remove empty elements from an array in Javascript
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ASP.NET Identity's default Password Hasher - How does it work and is it secure?
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Change date of git tag (or GitHub Release based on it)
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answered Feb 12 '14 at 23:06
PhrogzPhrogz
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What is the difference between Amazon S3 and Amazon EC2 instance?
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answered Jan 18 '13 at 4:28
David LevesqueDavid Levesque
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Bomb dropping algorithm
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edited Mar 9 '13 at 8:46
community wiki
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Setting an object to null vs Dispose()
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jmvtrinidad
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answered Feb 22 '09 at 9:47
Jon SkeetJon Skeet
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How to convert a number to string and vice versa in C++
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Accessing members of items in a JSONArray with Java
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idewz
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answered Oct 14 '09 at 20:32
notnoopnotnoop
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Multiple INSERT statements vs. single INSERT with multiple VALUES
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What does .SD stand for in data.table in R
...,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: 1 a1_b3_c5
# 2: 3 a2_b4_c6
Basically, the by=y statement breaks the orig...