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What's the fastest way to merge/join data.frames in R?
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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
> DF1
a b c
1 1 1 a
2 1 2 b
3 2 3 c
4 2 4 e
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Create a dictionary with list comprehension
...sion:
{key: value for (key, value) in iterable}
Note: this is for Python 3.x (and 2.7 upwards). Formerly in Python 2.6 and earlier, the dict built-in could receive an iterable of key/value pairs, so you can pass it a list comprehension or generator expression. For example:
dict((key, func(key)) fo...
What does the tilde (~) mean in my composer.json file?
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3 Answers
3
Active
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Python nonlocal statement
What does the Python nonlocal statement do (in Python 3.0 and later)?
9 Answers
9
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Force point (“.”) as decimal separator in java
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answered Mar 8 '11 at 17:32
Jon SkeetJon Skeet
1211k772772 gold badges85588558 silver badges88218821 bronze badges
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Algorithm to find Largest prime factor of a number
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134
Actually there are several more efficient ways to find factors of big numbers (for smaller ones...
Why is this jQuery click function not working?
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answered Sep 3 '13 at 22:14
mobiusmobius
4,68622 gold badges2424 silver badges3939 bronze badges
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Algorithms based on number base systems? [closed]
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39
Chris Okasaki has a very good chapter in his book Purely Functional Data Structures that discus...
What does “%” (percent) do in PowerShell?
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3 Answers
3
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List comprehension rebinds names even after scope of comprehension. Is this right?
...omprehensions leak the loop control variable in Python 2 but not in Python 3. Here's Guido van Rossum (creator of Python) explaining the history behind this:
We also made another change in Python
3, to improve equivalence between list
comprehensions and generator
expressions. In Python 2,...