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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...
Extract a substring from a string in Ruby using a regular expression
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edited Sep 24 '18 at 16:43
Iulian Onofrei
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Postgres: Distinct but only for one column
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answered Jun 4 '13 at 12:36
Clodoaldo NetoClodoaldo Neto
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Concatenate two slices in Go
I'm trying to combine the slice [1, 2] and the slice [3, 4] . How can I do this in Go?
7 Answers
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Find and replace string values in list
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answered Jun 28 '10 at 22:47
sberrysberry
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Why does make think the target is up to date?
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4 Answers
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Capturing Ctrl-c in ruby
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answered Jan 18 '10 at 21:46
Wayne ConradWayne Conrad
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What is the at sign (@) in a batch file and what does it do?
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Devil's Advocate
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answered Jan 12 '14 at 16:28
SunnySunny
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Start thread with member function
...ate type.
– Dave S
May 20 '12 at 13:49
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