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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...
Difference between two dates in Python
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Fred FooFred Foo
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Overload constructor for Scala's Case Classes?
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retronymretronym
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How do you clear a slice in Go?
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zzzzzzzz
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Regex to match a digit two or four times
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145
There's no specific syntax for that, but there are lots of ways to do it:
(?:\d{4}|\d{2}) &...
How to get default gateway in Mac OSX
...-n get www.yahoo.com
The output would be similar to:
route to: 98.137.149.56
destination: default
mask: 128.0.0.0
gateway: 5.5.0.1
interface: tun0
flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
recvpipe sendpipe ssthresh rtt,msec rttvar hopcount mtu expire
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Python list iterator behavior and next(iterator)
...10)))
>>> for i in a:
... print(i)
... next(a)
...
0
1
2
3
4
5
6
7
8
9
So 0 is the output of print(i), 1 the return value from next(), echoed by the interactive interpreter, etc. There are just 5 iterations, each iteration resulting in 2 lines being written to the terminal.
If you...
Rounding BigDecimal to *always* have two decimal places
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408
value = value.setScale(2, RoundingMode.CEILING)
...