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What's the fastest way to merge/join data.frames in R?
...s for duplicate keys. (continued after code)
DF1 = data.frame(a = c(1, 1, 2, 2), b = 1:4)
DF2 = data.frame(b = c(1, 2, 3, 3, 4), c = letters[1:5])
merge(DF1, DF2)
b a c
1 1 1 a
2 2 1 b
3 3 2 c
4 3 2 d
5 4 2 e
DF1$c = DF2$c[match(DF1$b, DF2$b)]
DF1$c
[1] a b c e
Levels: a b c d e
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What do the numbers in a version typically represent (i.e. v1.9.0.1)?
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28 Answers
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Algorithm for Determining Tic Tac Toe Game Over
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22 Answers
22
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Convert numpy array to tuple
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>>> arr = numpy.array(((2,2),(2,-2)))
>>> tuple(map(tuple, arr))
((2, 2), (2, -2))
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Mod in Java produces negative numbers [duplicate]
When I calculate int i = -1 % 2 I get -1 in Java. In Python, I get 1 as the result of -1 % 2 .
What do I have to do to get the same behavior in Java with the modulo function?
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Display number with leading zeros
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In Python 2 (and Python 3) you can do:
print "%02d" % (1,)
Basically % is like printf or sprintf (see docs).
For Python 3.+, the same behavior can also be achieved with format:
print("{:02d}".format(1))
For Python 3.6+ the s...
What is the difference between old style and new style classes in Python?
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From New-style and classic classes:
Up to Python 2.1, old-style classes were the only flavour available to the user.
The concept of (old-style) class is unrelated to the concept of type:
if x is an instance of an old-style class, then x.__class__
designates the cla...
Version of SQLite used in Android?
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UPDATE OCT 2016: Here is a link to the updated official docs which includes the main points in t...