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How to reorder data.table columns (without copying)
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185
Use setcolorder():
library(data.table)
x <- data.table(a = 1:3, b = 3:1, c = runif(3))
x
#...
How to get a specific output iterating a hash in Ruby?
...uts "#{key}-----"
puts array
end
Regarding order I should add, that in 1.8 the items will be iterated in random order (well, actually in an order defined by Fixnum's hashing function), while in 1.9 it will be iterated in the order of the literal.
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How can I delete one element from an array by value
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15 Answers
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Single Line Nested For Loops
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172
The best source of information is the official Python tutorial on list comprehensions. List c...
Find the max of two or more columns with pandas
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185
You can get the maximum like this:
>>> import pandas as pd
>>> df = pd.Data...
while (1) vs. while(True) — Why is there a difference (in python 2 bytecode)?
Intrigued by this question about infinite loops in perl: while (1) Vs. for (;;) Is there a speed difference? , I decided to run a similar comparison in python. I expected that the compiler would generate the same byte code for while(True): pass and while(1): pass , but this is actually not the c...
Why is [1,2] + [3,4] = “1,23,4” in JavaScript?
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13 Answers
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What is the significance of initializing direction arrays below with given values when developing ch
...we want to add onto its x and its y value to move it to a nearby location, 1,0 is east, -1,0 is west, 0,1 is south, 0,-1 is north and so on.
(Here I have said top left is 0,0 and bottom right is 4,4 and shown what move each index of the arrays will make from the central point, X, at 2,2.)
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pandas: filter rows of DataFrame with operator chaining
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14 Answers
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Pass a data.frame column name to a function
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109
You can just use the column name directly:
df <- data.frame(A=1:10, B=2:11, C=3:12)
fun1 &...